Merge pull request #3115 from ziglang/fix-field-alignment-kludge

fix field alignment kludge by implementing lazy values

7 files changed, 1683 insertions, 1008 deletions

diff --git a/src/all_types.hpp b/src/all_types.hpp
index 2394bcb73b..83dcb8ba10 100644
--- a/src/all_types.hpp
+++ b/src/all_types.hpp
@@ -47,6 +47,19 @@ struct ResultLocPeer;
 struct ResultLocPeerParent;
 struct ResultLocBitCast;
 
+enum PtrLen {
+    PtrLenUnknown,
+    PtrLenSingle,
+    PtrLenC,
+};
+
+enum UndefAllowed {
+    UndefOk,
+    UndefBad,
+    LazyOkNoUndef,
+    LazyOk,
+};
+
 enum X64CABIClass {
     X64CABIClass_Unknown,
     X64CABIClass_MEMORY,
@@ -69,9 +82,9 @@ struct IrExecutable {
     IrExecutable *source_exec;
     IrAnalyze *analysis;
     Scope *begin_scope;
+    ErrorMsg *first_err_trace_msg;
     ZigList<Tld *> tld_list;
 
-    bool invalid;
     bool is_inline;
     bool is_generic_instantiation;
     bool need_err_code_spill;
@@ -255,6 +268,7 @@ enum ConstValSpecial {
     ConstValSpecialRuntime,
     ConstValSpecialStatic,
     ConstValSpecialUndef,
+    ConstValSpecialLazy,
 };
 
 enum RuntimeHintErrorUnion {
@@ -291,6 +305,73 @@ struct ConstGlobalRefs {
     uint32_t align;
 };
 
+enum LazyValueId {
+    LazyValueIdInvalid,
+    LazyValueIdAlignOf,
+    LazyValueIdPtrType,
+    LazyValueIdOptType,
+    LazyValueIdSliceType,
+    LazyValueIdFnType,
+};
+
+struct LazyValue {
+    LazyValueId id;
+};
+
+struct LazyValueAlignOf {
+    LazyValue base;
+
+    IrAnalyze *ira;
+    IrInstruction *target_type;
+};
+
+struct LazyValueSliceType {
+    LazyValue base;
+
+    IrAnalyze *ira;
+    ZigType *elem_type;
+    IrInstruction *align_inst; // can be null
+
+    bool is_const;
+    bool is_volatile;
+    bool is_allowzero;
+};
+
+struct LazyValuePtrType {
+    LazyValue base;
+
+    IrAnalyze *ira;
+    IrInstruction *elem_type;
+    IrInstruction *align_inst; // can be null
+
+    PtrLen ptr_len;
+    uint32_t bit_offset_in_host;
+
+    uint32_t host_int_bytes;
+    bool is_const;
+    bool is_volatile;
+    bool is_allowzero;
+};
+
+struct LazyValueOptType {
+    LazyValue base;
+
+    IrAnalyze *ira;
+    IrInstruction *payload_type;
+};
+
+struct LazyValueFnType {
+    LazyValue base;
+
+    IrAnalyze *ira;
+    AstNode *proto_node;
+    IrInstruction **param_types;
+    IrInstruction *align_inst; // can be null
+    IrInstruction *return_type;
+
+    bool is_generic;
+};
+
 struct ConstExprValue {
     ZigType *type;
     ConstValSpecial special;
@@ -318,6 +399,7 @@ struct ConstExprValue {
         ConstPtrValue x_ptr;
         ConstArgTuple x_arg_tuple;
         Buf *x_enum_literal;
+        LazyValue *x_lazy;
 
         // populated if special == ConstValSpecialRuntime
         RuntimeHintErrorUnion rh_error_union;
@@ -364,6 +446,7 @@ enum TldResolution {
     TldResolutionUnresolved,
     TldResolutionResolving,
     TldResolutionInvalid,
+    TldResolutionOkLazy,
     TldResolutionOk,
 };
 
@@ -420,10 +503,12 @@ struct TypeEnumField {
 
 struct TypeUnionField {
     Buf *name;
+    ZigType *type_entry; // available after ResolveStatusSizeKnown
+    ConstExprValue *type_val; // available after ResolveStatusZeroBitsKnown
     TypeEnumField *enum_field;
-    ZigType *type_entry;
     AstNode *decl_node;
     uint32_t gen_index;
+    uint32_t align;
 };
 
 enum NodeType {
@@ -946,6 +1031,7 @@ struct AstNodeEnumLiteral {
 
 struct AstNode {
     enum NodeType type;
+    bool already_traced_this_node;
     size_t line;
     size_t column;
     ZigType *owner;
@@ -1041,12 +1127,6 @@ struct FnTypeId {
 uint32_t fn_type_id_hash(FnTypeId*);
 bool fn_type_id_eql(FnTypeId *a, FnTypeId *b);
 
-enum PtrLen {
-    PtrLenUnknown,
-    PtrLenSingle,
-    PtrLenC,
-};
-
 struct ZigTypePointer {
     ZigType *child_type;
     ZigType *slice_parent;
@@ -1057,6 +1137,7 @@ struct ZigTypePointer {
     bool is_const;
     bool is_volatile;
     bool allow_zero;
+    bool resolve_loop_flag_zero_bits;
 };
 
 struct ZigTypeInt {
@@ -1075,7 +1156,8 @@ struct ZigTypeArray {
 
 struct TypeStructField {
     Buf *name;
-    ZigType *type_entry;
+    ZigType *type_entry; // available after ResolveStatusSizeKnown
+    ConstExprValue *type_val; // available after ResolveStatusZeroBitsKnown
     size_t src_index;
     size_t gen_index;
     size_t offset; // byte offset from beginning of struct
@@ -1131,11 +1213,11 @@ struct ZigTypeStruct {
     ResolveStatus resolve_status;
 
     bool is_slice;
-    bool resolve_loop_flag; // set this flag temporarily to detect infinite loops
-    bool reported_infinite_err;
     // whether any of the fields require comptime
     // known after ResolveStatusZeroBitsKnown
     bool requires_comptime;
+    bool resolve_loop_flag_zero_bits;
+    bool resolve_loop_flag_other;
 };
 
 struct ZigTypeOptional {
@@ -1157,26 +1239,20 @@ struct ZigTypeErrorSet {
 
 struct ZigTypeEnum {
     AstNode *decl_node;
-    ContainerLayout layout;
-    uint32_t src_field_count;
     TypeEnumField *fields;
-    bool is_invalid; // true if any fields are invalid
     ZigType *tag_int_type;
 
     ScopeDecls *decls_scope;
 
-    // set this flag temporarily to detect infinite loops
-    bool embedded_in_current;
-    bool reported_infinite_err;
-    // whether we've finished resolving it
-    bool complete;
-
-    bool zero_bits_loop_flag;
-    bool zero_bits_known;
-
     LLVMValueRef name_function;
 
     HashMap<Buf *, TypeEnumField *, buf_hash, buf_eql_buf> fields_by_name;
+    uint32_t src_field_count;
+
+    ContainerLayout layout;
+    ResolveStatus resolve_status;
+
+    bool resolve_loop_flag;
 };
 
 uint32_t type_ptr_hash(const ZigType *ptr);
@@ -1189,7 +1265,7 @@ struct ZigTypeUnion {
     HashMap<Buf *, TypeUnionField *, buf_hash, buf_eql_buf> fields_by_name;
     ZigType *tag_type; // always an enum or null
     LLVMTypeRef union_llvm_type;
-    ZigType *most_aligned_union_member;
+    TypeUnionField *most_aligned_union_member;
     size_t gen_union_index;
     size_t gen_tag_index;
     size_t union_abi_size;
@@ -1201,11 +1277,11 @@ struct ZigTypeUnion {
     ResolveStatus resolve_status;
 
     bool have_explicit_tag_type;
-    bool resolve_loop_flag; // set this flag temporarily to detect infinite loops
-    bool reported_infinite_err;
     // whether any of the fields require comptime
     // the value is not valid until zero_bits_known == true
     bool requires_comptime;
+    bool resolve_loop_flag_zero_bits;
+    bool resolve_loop_flag_other;
 };
 
 struct FnGenParamInfo {
@@ -1717,6 +1793,7 @@ struct CodeGen {
     //////////////////////////// Runtime State
     LLVMModuleRef module;
     ZigList<ErrorMsg*> errors;
+    ErrorMsg *trace_err;
     LLVMBuilderRef builder;
     ZigLLVMDIBuilder *dbuilder;
     ZigLLVMDICompileUnit *compile_unit;
@@ -1769,7 +1846,6 @@ struct CodeGen {
     ZigList<Tld *> resolve_queue;
     size_t resolve_queue_index;
     ZigList<TimeEvent> timing_events;
-    ZigList<AstNode *> tld_ref_source_node_stack;
     ZigList<ZigFn *> inline_fns;
     ZigList<ZigFn *> test_fns;
     ZigList<ErrorTableEntry *> errors_by_index;
@@ -1854,7 +1930,6 @@ struct CodeGen {
     ZigFn *main_fn;
     ZigFn *panic_fn;
     TldFn *panic_tld_fn;
-    AstNode *root_export_decl;
 
     WantPIC want_pic;
     WantStackCheck want_stack_check;
@@ -1942,7 +2017,7 @@ struct CodeGen {
     Buf *zig_lib_dir;
     Buf *zig_std_dir;
     Buf *dynamic_linker_path;
-    Buf *version_script_path; 
+    Buf *version_script_path;
 
     const char **llvm_argv;
     size_t llvm_argv_len;
@@ -3659,13 +3734,13 @@ enum ResultLocId {
     ResultLocIdBitCast,
 };
 
-// Additions to this struct may need to be handled in 
+// Additions to this struct may need to be handled in
 // ir_reset_result
 struct ResultLoc {
     ResultLocId id;
     bool written;
     bool allow_write_through_const;
-    IrInstruction *resolved_loc; // result ptr 
+    IrInstruction *resolved_loc; // result ptr
     IrInstruction *source_instruction;
     IrInstruction *gen_instruction; // value to store to the result loc
     ZigType *implicit_elem_type;
diff --git a/src/analyze.cpp b/src/analyze.cpp
index 35c598ab97..e0223dd9f7 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -20,7 +20,7 @@
 
 static const size_t default_backward_branch_quota = 1000;
 
-static Error resolve_struct_type(CodeGen *g, ZigType *struct_type);
+static Error ATTRIBUTE_MUST_USE resolve_struct_type(CodeGen *g, ZigType *struct_type);
 
 static Error ATTRIBUTE_MUST_USE resolve_struct_zero_bits(CodeGen *g, ZigType *struct_type);
 static Error ATTRIBUTE_MUST_USE resolve_struct_alignment(CodeGen *g, ZigType *struct_type);
@@ -59,13 +59,15 @@ ErrorMsg *add_token_error(CodeGen *g, ZigType *owner, Token *token, Buf *msg) {
             root_struct->source_code, root_struct->line_offsets, msg);
 
     g->errors.append(err);
+    g->trace_err = err;
     return err;
 }
 
-ErrorMsg *add_node_error(CodeGen *g, const AstNode *node, Buf *msg) {
+ErrorMsg *add_node_error(CodeGen *g, AstNode *node, Buf *msg) {
     Token fake_token;
     fake_token.start_line = node->line;
     fake_token.start_column = node->column;
+    node->already_traced_this_node = true;
     return add_token_error(g, node->owner, &fake_token, msg);
 }
 
@@ -271,6 +273,8 @@ bool type_is_resolved(ZigType *type_entry, ResolveStatus status) {
             return type_entry->data.structure.resolve_status >= status;
         case ZigTypeIdUnion:
             return type_entry->data.unionation.resolve_status >= status;
+        case ZigTypeIdEnum:
+            return type_entry->data.enumeration.resolve_status >= status;
         case ZigTypeIdFnFrame:
             switch (status) {
                 case ResolveStatusInvalid:
@@ -285,32 +289,28 @@ bool type_is_resolved(ZigType *type_entry, ResolveStatus status) {
                 case ResolveStatusLLVMFull:
                     return type_entry->llvm_type != nullptr;
             }
-        case ZigTypeIdEnum:
+        case ZigTypeIdOpaque:
+            return status < ResolveStatusSizeKnown;
+        case ZigTypeIdPointer:
             switch (status) {
-                case ResolveStatusUnstarted:
-                    return true;
                 case ResolveStatusInvalid:
                     zig_unreachable();
+                case ResolveStatusUnstarted:
+                    return true;
                 case ResolveStatusZeroBitsKnown:
-                    return type_entry->data.enumeration.zero_bits_known;
                 case ResolveStatusAlignmentKnown:
-                    return type_entry->data.enumeration.zero_bits_known;
                 case ResolveStatusSizeKnown:
-                    return type_entry->data.enumeration.complete;
+                    return type_entry->abi_size != SIZE_MAX;
                 case ResolveStatusLLVMFwdDecl:
                 case ResolveStatusLLVMFull:
-                    return type_entry->llvm_di_type != nullptr;
+                    return type_entry->llvm_type != nullptr;
             }
-            zig_unreachable();
-        case ZigTypeIdOpaque:
-            return status < ResolveStatusSizeKnown;
         case ZigTypeIdMetaType:
         case ZigTypeIdVoid:
         case ZigTypeIdBool:
         case ZigTypeIdUnreachable:
         case ZigTypeIdInt:
         case ZigTypeIdFloat:
-        case ZigTypeIdPointer:
         case ZigTypeIdArray:
         case ZigTypeIdComptimeFloat:
         case ZigTypeIdComptimeInt:
@@ -460,8 +460,6 @@ ZigType *get_pointer_to_type_extra(CodeGen *g, ZigType *child_type, bool is_cons
         }
     }
 
-    assert(type_is_resolved(child_type, ResolveStatusZeroBitsKnown));
-
     ZigType *entry = new_type_table_entry(ZigTypeIdPointer);
 
     const char *star_str = ptr_len_to_star_str(ptr_len);
@@ -491,17 +489,21 @@ ZigType *get_pointer_to_type_extra(CodeGen *g, ZigType *child_type, bool is_cons
                 buf_ptr(&child_type->name));
     }
 
-    assert(child_type->id != ZigTypeIdInvalid);
-
-    if (type_has_bits(child_type)) {
-        entry->abi_size = g->builtin_types.entry_usize->abi_size;
-        entry->size_in_bits = g->builtin_types.entry_usize->size_in_bits;
-        entry->abi_align = g->builtin_types.entry_usize->abi_align;
+    if (type_is_resolved(child_type, ResolveStatusZeroBitsKnown)) {
+        if (type_has_bits(child_type)) {
+            entry->abi_size = g->builtin_types.entry_usize->abi_size;
+            entry->size_in_bits = g->builtin_types.entry_usize->size_in_bits;
+            entry->abi_align = g->builtin_types.entry_usize->abi_align;
+        } else {
+            assert(byte_alignment == 0);
+            entry->abi_size = 0;
+            entry->size_in_bits = 0;
+            entry->abi_align = 0;
+        }
     } else {
-        assert(byte_alignment == 0);
-        entry->abi_size = 0;
-        entry->size_in_bits = 0;
-        entry->abi_align = 0;
+        entry->abi_size = SIZE_MAX;
+        entry->size_in_bits = SIZE_MAX;
+        entry->abi_align = UINT32_MAX;
     }
 
     entry->data.pointer.ptr_len = ptr_len;
@@ -865,7 +867,7 @@ ZigType *get_fn_type(CodeGen *g, FnTypeId *fn_type_id) {
         return table_entry->value;
     }
     if (fn_type_id->return_type != nullptr) {
-        if ((err = ensure_complete_type(g, fn_type_id->return_type)))
+        if ((err = type_resolve(g, fn_type_id->return_type, ResolveStatusSizeKnown)))
             return g->builtin_types.entry_invalid;
         assert(fn_type_id->return_type->id != ZigTypeIdOpaque);
     } else {
@@ -960,31 +962,209 @@ ZigType *get_partial_container_type(CodeGen *g, Scope *scope, ContainerKind kind
     return entry;
 }
 
-ConstExprValue *analyze_const_value(CodeGen *g, Scope *scope, AstNode *node, ZigType *type_entry, Buf *type_name) {
+ConstExprValue *analyze_const_value(CodeGen *g, Scope *scope, AstNode *node, ZigType *type_entry,
+        Buf *type_name, UndefAllowed undef)
+{
     size_t backward_branch_count = 0;
     size_t backward_branch_quota = default_backward_branch_quota;
     return ir_eval_const_value(g, scope, node, type_entry,
             &backward_branch_count, &backward_branch_quota,
-            nullptr, nullptr, node, type_name, nullptr, nullptr);
+            nullptr, nullptr, node, type_name, nullptr, nullptr, undef);
 }
 
-ZigType *analyze_type_expr(CodeGen *g, Scope *scope, AstNode *node) {
-    ConstExprValue *result = analyze_const_value(g, scope, node, g->builtin_types.entry_type, nullptr);
-    if (type_is_invalid(result->type))
-        return g->builtin_types.entry_invalid;
+static Error type_val_resolve_zero_bits(CodeGen *g, ConstExprValue *type_val, ZigType *parent_type,
+        ConstExprValue *parent_type_val, bool *is_zero_bits)
+{
+    Error err;
+    if (type_val->special != ConstValSpecialLazy) {
+        assert(type_val->special == ConstValSpecialStatic);
+        if ((type_val->data.x_type->id == ZigTypeIdStruct &&
+            type_val->data.x_type->data.structure.resolve_loop_flag_zero_bits) ||
+            (type_val->data.x_type->id == ZigTypeIdUnion &&
+             type_val->data.x_type->data.unionation.resolve_loop_flag_zero_bits) ||
+            type_val->data.x_type->id == ZigTypeIdPointer)
+        {
+            // Does a struct/union which contains a pointer field to itself have bits? Yes.
+            *is_zero_bits = false;
+            return ErrorNone;
+        }
+        if ((err = type_resolve(g, type_val->data.x_type, ResolveStatusZeroBitsKnown)))
+            return err;
+        *is_zero_bits = (type_val->data.x_type->abi_size == 0);
+        return ErrorNone;
+    }
+    switch (type_val->data.x_lazy->id) {
+        case LazyValueIdInvalid:
+        case LazyValueIdAlignOf:
+            zig_unreachable();
+        case LazyValueIdPtrType: {
+            LazyValuePtrType *lazy_ptr_type = reinterpret_cast<LazyValuePtrType *>(type_val->data.x_lazy);
 
-    assert(result->special != ConstValSpecialRuntime);
-    // Reject undefined as valid `type` type even though the specification
-    // allows it to be casted to anything.
-    // See also ir_resolve_type()
-    if (result->special == ConstValSpecialUndef) {
-        add_node_error(g, node,
-            buf_sprintf("expected type 'type', found '%s'",
-                buf_ptr(&g->builtin_types.entry_undef->name)));
-        return g->builtin_types.entry_invalid;
+            if (parent_type_val == &lazy_ptr_type->elem_type->value) {
+                // Does a struct which contains a pointer field to itself have bits? Yes.
+                *is_zero_bits = false;
+                return ErrorNone;
+            } else {
+                if (parent_type_val == nullptr) {
+                    parent_type_val = type_val;
+                }
+                return type_val_resolve_zero_bits(g, &lazy_ptr_type->elem_type->value, parent_type,
+                        parent_type_val, is_zero_bits);
+            }
+        }
+        case LazyValueIdOptType:
+        case LazyValueIdSliceType:
+            *is_zero_bits = false;
+            return ErrorNone;
+        case LazyValueIdFnType: {
+            LazyValueFnType *lazy_fn_type = reinterpret_cast<LazyValueFnType *>(type_val->data.x_lazy);
+            *is_zero_bits = lazy_fn_type->is_generic;
+            return ErrorNone;
+        }
+    }
+    zig_unreachable();
+}
+
+Error type_val_resolve_is_opaque_type(CodeGen *g, ConstExprValue *type_val, bool *is_opaque_type) {
+    if (type_val->special != ConstValSpecialLazy) {
+        assert(type_val->special == ConstValSpecialStatic);
+        *is_opaque_type = (type_val->data.x_type->id == ZigTypeIdOpaque);
+        return ErrorNone;
+    }
+    switch (type_val->data.x_lazy->id) {
+        case LazyValueIdInvalid:
+        case LazyValueIdAlignOf:
+            zig_unreachable();
+        case LazyValueIdSliceType:
+        case LazyValueIdPtrType:
+        case LazyValueIdFnType:
+        case LazyValueIdOptType:
+            *is_opaque_type = false;
+            return ErrorNone;
     }
+    zig_unreachable();
+}
 
-    assert(result->data.x_type != nullptr);
+static ReqCompTime type_val_resolve_requires_comptime(CodeGen *g, ConstExprValue *type_val) {
+    if (type_val->special != ConstValSpecialLazy) {
+        return type_requires_comptime(g, type_val->data.x_type);
+    }
+    switch (type_val->data.x_lazy->id) {
+        case LazyValueIdInvalid:
+        case LazyValueIdAlignOf:
+            zig_unreachable();
+        case LazyValueIdSliceType: {
+            LazyValueSliceType *lazy_slice_type = reinterpret_cast<LazyValueSliceType *>(type_val->data.x_lazy);
+            if (type_is_invalid(lazy_slice_type->elem_type))
+                return ReqCompTimeInvalid;
+            return type_requires_comptime(g, lazy_slice_type->elem_type);
+        }
+        case LazyValueIdPtrType: {
+            LazyValuePtrType *lazy_ptr_type = reinterpret_cast<LazyValuePtrType *>(type_val->data.x_lazy);
+            return type_val_resolve_requires_comptime(g, &lazy_ptr_type->elem_type->value);
+        }
+        case LazyValueIdOptType: {
+            LazyValueOptType *lazy_opt_type = reinterpret_cast<LazyValueOptType *>(type_val->data.x_lazy);
+            return type_val_resolve_requires_comptime(g, &lazy_opt_type->payload_type->value);
+        }
+        case LazyValueIdFnType: {
+            LazyValueFnType *lazy_fn_type = reinterpret_cast<LazyValueFnType *>(type_val->data.x_lazy);
+            if (lazy_fn_type->is_generic)
+                return ReqCompTimeYes;
+            switch (type_val_resolve_requires_comptime(g, &lazy_fn_type->return_type->value)) {
+                case ReqCompTimeInvalid:
+                    return ReqCompTimeInvalid;
+                case ReqCompTimeYes:
+                    return ReqCompTimeYes;
+                case ReqCompTimeNo:
+                    break;
+            }
+            size_t param_count = lazy_fn_type->proto_node->data.fn_proto.params.length;
+            for (size_t i = 0; i < param_count; i += 1) {
+                AstNode *param_node = lazy_fn_type->proto_node->data.fn_proto.params.at(i);
+                bool param_is_var_args = param_node->data.param_decl.is_var_args;
+                if (param_is_var_args) break;
+                switch (type_val_resolve_requires_comptime(g, &lazy_fn_type->param_types[i]->value)) {
+                    case ReqCompTimeInvalid:
+                        return ReqCompTimeInvalid;
+                    case ReqCompTimeYes:
+                        return ReqCompTimeYes;
+                    case ReqCompTimeNo:
+                        break;
+                }
+            }
+            return ReqCompTimeNo;
+        }
+    }
+    zig_unreachable();
+}
+
+Error type_val_resolve_abi_align(CodeGen *g, ConstExprValue *type_val, uint32_t *abi_align) {
+    Error err;
+    if (type_val->special != ConstValSpecialLazy) {
+        assert(type_val->special == ConstValSpecialStatic);
+        ZigType *ty = type_val->data.x_type;
+        if (ty->id == ZigTypeIdPointer) {
+            *abi_align = g->builtin_types.entry_usize->abi_align;
+            return ErrorNone;
+        }
+        if ((err = type_resolve(g, ty, ResolveStatusAlignmentKnown)))
+            return err;
+        *abi_align = ty->abi_align;
+        return ErrorNone;
+    }
+    switch (type_val->data.x_lazy->id) {
+        case LazyValueIdInvalid:
+        case LazyValueIdAlignOf:
+            zig_unreachable();
+        case LazyValueIdSliceType:
+        case LazyValueIdPtrType:
+        case LazyValueIdFnType:
+            *abi_align = g->builtin_types.entry_usize->abi_align;
+            return ErrorNone;
+        case LazyValueIdOptType: {
+            LazyValueOptType *lazy_opt_type = reinterpret_cast<LazyValueOptType *>(type_val->data.x_lazy);
+            return type_val_resolve_abi_align(g, &lazy_opt_type->payload_type->value, abi_align);
+        }
+    }
+    zig_unreachable();
+}
+
+static OnePossibleValue type_val_resolve_has_one_possible_value(CodeGen *g, ConstExprValue *type_val) {
+    if (type_val->special != ConstValSpecialLazy) {
+        return type_has_one_possible_value(g, type_val->data.x_type);
+    }
+    switch (type_val->data.x_lazy->id) {
+        case LazyValueIdInvalid:
+        case LazyValueIdAlignOf:
+            zig_unreachable();
+        case LazyValueIdSliceType: // it has the len field
+        case LazyValueIdOptType: // it has the optional bit
+        case LazyValueIdFnType:
+            return OnePossibleValueNo;
+        case LazyValueIdPtrType: {
+            Error err;
+            bool zero_bits;
+            if ((err = type_val_resolve_zero_bits(g, type_val, nullptr, nullptr, &zero_bits))) {
+                return OnePossibleValueInvalid;
+            }
+            if (zero_bits) {
+                return OnePossibleValueYes;
+            } else {
+                return OnePossibleValueNo;
+            }
+        }
+    }
+    zig_unreachable();
+}
+
+ZigType *analyze_type_expr(CodeGen *g, Scope *scope, AstNode *node) {
+    ConstExprValue *result = analyze_const_value(g, scope, node, g->builtin_types.entry_type,
+            nullptr, UndefBad);
+    if (type_is_invalid(result->type))
+        return g->builtin_types.entry_invalid;
+    src_assert(result->special == ConstValSpecialStatic, node);
+    src_assert(result->data.x_type != nullptr, node);
     return result->data.x_type;
 }
 
@@ -1032,7 +1212,8 @@ void init_fn_type_id(FnTypeId *fn_type_id, AstNode *proto_node, size_t param_cou
 }
 
 static bool analyze_const_align(CodeGen *g, Scope *scope, AstNode *node, uint32_t *result) {
-    ConstExprValue *align_result = analyze_const_value(g, scope, node, get_align_amt_type(g), nullptr);
+    ConstExprValue *align_result = analyze_const_value(g, scope, node, get_align_amt_type(g),
+            nullptr, UndefBad);
     if (type_is_invalid(align_result->type))
         return false;
 
@@ -1054,7 +1235,7 @@ static bool analyze_const_string(CodeGen *g, Scope *scope, AstNode *node, Buf **
     ZigType *ptr_type = get_pointer_to_type_extra(g, g->builtin_types.entry_u8, true, false,
             PtrLenUnknown, 0, 0, 0, false);
     ZigType *str_type = get_slice_type(g, ptr_type);
-    ConstExprValue *result_val = analyze_const_value(g, scope, node, str_type, nullptr);
+    ConstExprValue *result_val = analyze_const_value(g, scope, node, str_type, nullptr, UndefBad);
     if (type_is_invalid(result_val->type))
         return false;
 
@@ -1404,7 +1585,6 @@ static ZigType *analyze_fn_type(CodeGen *g, AstNode *proto_node, Scope *child_sc
         add_node_error(g, proto_node,
             buf_sprintf("TODO implement inferred return types https://github.com/ziglang/zig/issues/447"));
         return g->builtin_types.entry_invalid;
-        //return get_generic_fn_type(g, &fn_type_id);
     }
 
     ZigType *specified_return_type = analyze_type_expr(g, child_scope, fn_proto->return_type);
@@ -1423,14 +1603,17 @@ static ZigType *analyze_fn_type(CodeGen *g, AstNode *proto_node, Scope *child_sc
     }
 
     if (!calling_convention_allows_zig_types(fn_type_id.cc) &&
-        fn_type_id.return_type->id != ZigTypeIdVoid &&
-        !type_allowed_in_extern(g, fn_type_id.return_type))
+        fn_type_id.return_type->id != ZigTypeIdVoid)
     {
-        add_node_error(g, fn_proto->return_type,
-                buf_sprintf("return type '%s' not allowed in function with calling convention '%s'",
-                    buf_ptr(&fn_type_id.return_type->name),
-                    calling_convention_name(fn_type_id.cc)));
-        return g->builtin_types.entry_invalid;
+        if ((err = type_resolve(g, fn_type_id.return_type, ResolveStatusSizeKnown)))
+            return g->builtin_types.entry_invalid;
+        if (!type_allowed_in_extern(g, fn_type_id.return_type)) {
+            add_node_error(g, fn_proto->return_type,
+                    buf_sprintf("return type '%s' not allowed in function with calling convention '%s'",
+                        buf_ptr(&fn_type_id.return_type->name),
+                        calling_convention_name(fn_type_id.cc)));
+            return g->builtin_types.entry_invalid;
+        }
     }
 
     switch (fn_type_id.return_type->id) {
@@ -1490,7 +1673,7 @@ bool type_is_invalid(ZigType *type_entry) {
         case ZigTypeIdUnion:
             return type_entry->data.unionation.resolve_status == ResolveStatusInvalid;
         case ZigTypeIdEnum:
-            return type_entry->data.enumeration.is_invalid;
+            return type_entry->data.enumeration.resolve_status == ResolveStatusInvalid;
         default:
             return false;
     }
@@ -1599,12 +1782,11 @@ static Error resolve_struct_type(CodeGen *g, ZigType *struct_type) {
 
     AstNode *decl_node = struct_type->data.structure.decl_node;
 
-    if (struct_type->data.structure.resolve_loop_flag) {
+    if (struct_type->data.structure.resolve_loop_flag_other) {
         if (struct_type->data.structure.resolve_status != ResolveStatusInvalid) {
             struct_type->data.structure.resolve_status = ResolveStatusInvalid;
-            ErrorMsg *msg = add_node_error(g, decl_node,
-                buf_sprintf("struct '%s' contains itself", buf_ptr(&struct_type->name)));
-            emit_error_notes_for_ref_stack(g, msg);
+            add_node_error(g, decl_node,
+                buf_sprintf("struct '%s' depends on itself", buf_ptr(&struct_type->name)));
         }
         return ErrorSemanticAnalyzeFail;
     }
@@ -1615,18 +1797,42 @@ static Error resolve_struct_type(CodeGen *g, ZigType *struct_type) {
     size_t field_count = struct_type->data.structure.src_field_count;
 
     bool packed = (struct_type->data.structure.layout == ContainerLayoutPacked);
-    struct_type->data.structure.resolve_loop_flag = true;
+    struct_type->data.structure.resolve_loop_flag_other = true;
 
     uint32_t *host_int_bytes = packed ? allocate<uint32_t>(struct_type->data.structure.gen_field_count) : nullptr;
 
-    // Resolve sizes of all the field types. Done before the offset loop because the offset
-    // loop has to look ahead.
+    // Resolve types for fields and then resolve sizes of all the field types.
+    // This is done before the offset loop because the offset loop has to look ahead.
     for (size_t i = 0; i < field_count; i += 1) {
+        AstNode *field_source_node = decl_node->data.container_decl.fields.at(i);
         TypeStructField *field = &struct_type->data.structure.fields[i];
+
+        if ((err = ir_resolve_lazy(g, field_source_node, field->type_val))) {
+            struct_type->data.structure.resolve_status = ResolveStatusInvalid;
+            return err;
+        }
+        field->type_entry = field->type_val->data.x_type;
+
         if ((err = type_resolve(g, field->type_entry, ResolveStatusSizeKnown))) {
             struct_type->data.structure.resolve_status = ResolveStatusInvalid;
+            return err;
+        }
+
+        if (struct_type->data.structure.layout == ContainerLayoutExtern &&
+            !type_allowed_in_extern(g, field->type_entry))
+        {
+            add_node_error(g, field_source_node,
+                    buf_sprintf("extern structs cannot contain fields of type '%s'",
+                        buf_ptr(&field->type_entry->name)));
+            struct_type->data.structure.resolve_status = ResolveStatusInvalid;
             return ErrorSemanticAnalyzeFail;
+        } else if (packed) {
+            if ((err = emit_error_unless_type_allowed_in_packed_struct(g, field->type_entry, field_source_node))) {
+                struct_type->data.structure.resolve_status = ResolveStatusInvalid;
+                return err;
+            }
         }
+
     }
 
     size_t packed_bits_offset = 0;
@@ -1690,9 +1896,9 @@ static Error resolve_struct_type(CodeGen *g, ZigType *struct_type) {
                     break;
                 }
             }
-            size_t next_abi_align = (next_src_field_index == field_count) ?
-                abi_align : struct_type->data.structure.fields[next_src_field_index].type_entry->abi_align;
-            next_offset = next_field_offset(next_offset, abi_align, field_type->abi_size, next_abi_align);
+            size_t next_align = (next_src_field_index == field_count) ?
+                abi_align : struct_type->data.structure.fields[next_src_field_index].align;
+            next_offset = next_field_offset(next_offset, abi_align, field_type->abi_size, next_align);
             size_in_bits = next_offset * 8;
         }
     }
@@ -1708,7 +1914,7 @@ static Error resolve_struct_type(CodeGen *g, ZigType *struct_type) {
     struct_type->size_in_bits = size_in_bits;
     struct_type->data.structure.resolve_status = ResolveStatusSizeKnown;
     struct_type->data.structure.gen_field_count = (uint32_t)gen_field_index;
-    struct_type->data.structure.resolve_loop_flag = false;
+    struct_type->data.structure.resolve_loop_flag_other = false;
     struct_type->data.structure.host_int_bytes = host_int_bytes;
 
     return ErrorNone;
@@ -1728,22 +1934,21 @@ static Error resolve_union_alignment(CodeGen *g, ZigType *union_type) {
     if (union_type->data.unionation.resolve_status >= ResolveStatusAlignmentKnown)
         return ErrorNone;
 
-    if (union_type->data.unionation.resolve_loop_flag) {
-        if (!union_type->data.unionation.reported_infinite_err) {
-            AstNode *decl_node = union_type->data.unionation.decl_node;
-            union_type->data.unionation.reported_infinite_err = true;
+    AstNode *decl_node = union_type->data.structure.decl_node;
+
+    if (union_type->data.unionation.resolve_loop_flag_other) {
+        if (union_type->data.unionation.resolve_status != ResolveStatusInvalid) {
             union_type->data.unionation.resolve_status = ResolveStatusInvalid;
-            ErrorMsg *msg = add_node_error(g, decl_node,
-                    buf_sprintf("union '%s' contains itself", buf_ptr(&union_type->name)));
-            emit_error_notes_for_ref_stack(g, msg);
+            add_node_error(g, decl_node,
+                buf_sprintf("union '%s' depends on itself", buf_ptr(&union_type->name)));
         }
         return ErrorSemanticAnalyzeFail;
     }
 
     // set temporary flag
-    union_type->data.unionation.resolve_loop_flag = true;
+    union_type->data.unionation.resolve_loop_flag_other = true;
 
-    ZigType *most_aligned_union_member = nullptr;
+    TypeUnionField *most_aligned_union_member = nullptr;
     uint32_t field_count = union_type->data.unionation.src_field_count;
     bool packed = union_type->data.unionation.layout == ContainerLayoutPacked;
 
@@ -1752,34 +1957,40 @@ static Error resolve_union_alignment(CodeGen *g, ZigType *union_type) {
         if (field->gen_index == UINT32_MAX)
             continue;
 
-        size_t this_field_align;
-        if (packed) {
-            // TODO: https://github.com/ziglang/zig/issues/1512
-            this_field_align = 1;
-        // This is the same hack as resolve_struct_alignment. See the comment there.
-        } else if (field->type_entry == nullptr) {
-            this_field_align = g->builtin_types.entry_usize->abi_align;
-        } else {
+        AstNode *align_expr = field->decl_node->data.struct_field.align_expr;
+        if (align_expr != nullptr) {
+            if (!analyze_const_align(g, &union_type->data.unionation.decls_scope->base, align_expr,
+                        &field->align))
+            {
+                union_type->data.unionation.resolve_status = ResolveStatusInvalid;
+                return err;
+            }
+            add_node_error(g, field->decl_node,
+                buf_create_from_str("TODO implement field alignment syntax for unions. https://github.com/ziglang/zig/issues/3125"));
+        } else if (packed) {
+            field->align = 1;
+        } else if (field->type_entry != nullptr) {
             if ((err = type_resolve(g, field->type_entry, ResolveStatusAlignmentKnown))) {
                 union_type->data.unionation.resolve_status = ResolveStatusInvalid;
-                return ErrorSemanticAnalyzeFail;
+                return err;
+            }
+            field->align = field->type_entry->abi_align;
+        } else {
+            if ((err = type_val_resolve_abi_align(g, field->type_val, &field->align))) {
+                union_type->data.unionation.resolve_status = ResolveStatusInvalid;
+                return err;
             }
-
             if (union_type->data.unionation.resolve_status == ResolveStatusInvalid)
                 return ErrorSemanticAnalyzeFail;
-
-            this_field_align = field->type_entry->abi_align;
         }
 
-        if (most_aligned_union_member == nullptr ||
-            this_field_align > most_aligned_union_member->abi_align)
-        {
-            most_aligned_union_member = field->type_entry;
+        if (most_aligned_union_member == nullptr || field->align > most_aligned_union_member->align) {
+            most_aligned_union_member = field;
         }
     }
 
     // unset temporary flag
-    union_type->data.unionation.resolve_loop_flag = false;
+    union_type->data.unionation.resolve_loop_flag_other = false;
     union_type->data.unionation.resolve_status = ResolveStatusAlignmentKnown;
     union_type->data.unionation.most_aligned_union_member = most_aligned_union_member;
 
@@ -1793,18 +2004,18 @@ static Error resolve_union_alignment(CodeGen *g, ZigType *union_type) {
             union_type->abi_align = tag_type->abi_align;
             union_type->data.unionation.gen_tag_index = SIZE_MAX;
             union_type->data.unionation.gen_union_index = SIZE_MAX;
-        } else if (tag_type->abi_align > most_aligned_union_member->abi_align) {
+        } else if (tag_type->abi_align > most_aligned_union_member->align) {
             union_type->abi_align = tag_type->abi_align;
             union_type->data.unionation.gen_tag_index = 0;
             union_type->data.unionation.gen_union_index = 1;
         } else {
-            union_type->abi_align = most_aligned_union_member->abi_align;
+            union_type->abi_align = most_aligned_union_member->align;
             union_type->data.unionation.gen_union_index = 0;
             union_type->data.unionation.gen_tag_index = 1;
         }
     } else {
         assert(most_aligned_union_member != nullptr);
-        union_type->abi_align = most_aligned_union_member->abi_align;
+        union_type->abi_align = most_aligned_union_member->align;
         union_type->data.unionation.gen_union_index = SIZE_MAX;
         union_type->data.unionation.gen_tag_index = SIZE_MAX;
     }
@@ -1812,6 +2023,17 @@ static Error resolve_union_alignment(CodeGen *g, ZigType *union_type) {
     return ErrorNone;
 }
 
+ZigType *resolve_union_field_type(CodeGen *g, TypeUnionField *union_field) {
+    Error err;
+    if (union_field->type_entry == nullptr) {
+        if ((err = ir_resolve_lazy(g, union_field->decl_node, union_field->type_val))) {
+            return nullptr;
+        }
+        union_field->type_entry = union_field->type_val->data.x_type;
+    }
+    return union_field->type_entry;
+}
+
 static Error resolve_union_type(CodeGen *g, ZigType *union_type) {
     assert(union_type->id == ZigTypeIdUnion);
 
@@ -1831,30 +2053,32 @@ static Error resolve_union_type(CodeGen *g, ZigType *union_type) {
     assert(decl_node->type == NodeTypeContainerDecl);
 
     uint32_t field_count = union_type->data.unionation.src_field_count;
-    ZigType *most_aligned_union_member = union_type->data.unionation.most_aligned_union_member;
+    TypeUnionField *most_aligned_union_member = union_type->data.unionation.most_aligned_union_member;
 
     assert(union_type->data.unionation.fields);
 
     size_t union_abi_size = 0;
     size_t union_size_in_bits = 0;
 
-    if (union_type->data.unionation.resolve_loop_flag) {
-        if (!union_type->data.unionation.reported_infinite_err) {
-            union_type->data.unionation.reported_infinite_err = true;
+    if (union_type->data.unionation.resolve_loop_flag_other) {
+        if (union_type->data.unionation.resolve_status != ResolveStatusInvalid) {
             union_type->data.unionation.resolve_status = ResolveStatusInvalid;
-            ErrorMsg *msg = add_node_error(g, decl_node,
-                    buf_sprintf("union '%s' depends on its own size", buf_ptr(&union_type->name)));
-            emit_error_notes_for_ref_stack(g, msg);
+            add_node_error(g, decl_node,
+                buf_sprintf("union '%s' depends on itself", buf_ptr(&union_type->name)));
         }
         return ErrorSemanticAnalyzeFail;
     }
 
     // set temporary flag
-    union_type->data.unionation.resolve_loop_flag = true;
+    union_type->data.unionation.resolve_loop_flag_other = true;
 
     for (uint32_t i = 0; i < field_count; i += 1) {
         TypeUnionField *union_field = &union_type->data.unionation.fields[i];
-        ZigType *field_type = union_field->type_entry;
+        ZigType *field_type = resolve_union_field_type(g, union_field);
+        if (field_type == nullptr) {
+            union_type->data.unionation.resolve_status = ResolveStatusInvalid;
+            return ErrorSemanticAnalyzeFail;
+        }
 
         if ((err = type_resolve(g, field_type, ResolveStatusSizeKnown))) {
             union_type->data.unionation.resolve_status = ResolveStatusInvalid;
@@ -1874,11 +2098,11 @@ static Error resolve_union_type(CodeGen *g, ZigType *union_type) {
     // The union itself for now has to be treated as being independently aligned.
     // See https://github.com/ziglang/zig/issues/2166.
     if (most_aligned_union_member != nullptr) {
-        union_abi_size = align_forward(union_abi_size, most_aligned_union_member->abi_align);
+        union_abi_size = align_forward(union_abi_size, most_aligned_union_member->align);
     }
 
     // unset temporary flag
-    union_type->data.unionation.resolve_loop_flag = false;
+    union_type->data.unionation.resolve_loop_flag_other = false;
     union_type->data.unionation.resolve_status = ResolveStatusSizeKnown;
     union_type->data.unionation.union_abi_size = union_abi_size;
 
@@ -1897,7 +2121,7 @@ static Error resolve_union_type(CodeGen *g, ZigType *union_type) {
             field_sizes[union_type->data.unionation.gen_tag_index] = tag_type->abi_size;
             field_aligns[union_type->data.unionation.gen_tag_index] = tag_type->abi_align;
             field_sizes[union_type->data.unionation.gen_union_index] = union_abi_size;
-            field_aligns[union_type->data.unionation.gen_union_index] = most_aligned_union_member->abi_align;
+            field_aligns[union_type->data.unionation.gen_union_index] = most_aligned_union_member->align;
             size_t field2_offset = next_field_offset(0, union_type->abi_align, field_sizes[0], field_aligns[1]);
             union_type->abi_size = next_field_offset(field2_offset, union_type->abi_align, field_sizes[1], union_type->abi_align);
             union_type->size_in_bits = union_type->abi_size * 8;
@@ -1925,24 +2149,25 @@ static bool type_is_valid_extern_enum_tag(CodeGen *g, ZigType *ty) {
 static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
     assert(enum_type->id == ZigTypeIdEnum);
 
-    if (enum_type->data.enumeration.is_invalid)
+    if (enum_type->data.enumeration.resolve_status == ResolveStatusInvalid)
         return ErrorSemanticAnalyzeFail;
-
-    if (enum_type->data.enumeration.zero_bits_known)
+    if (enum_type->data.enumeration.resolve_status >= ResolveStatusZeroBitsKnown)
         return ErrorNone;
 
-    if (enum_type->data.enumeration.zero_bits_loop_flag) {
-        ErrorMsg *msg = add_node_error(g, enum_type->data.enumeration.decl_node,
-            buf_sprintf("'%s' depends on itself", buf_ptr(&enum_type->name)));
-        emit_error_notes_for_ref_stack(g, msg);
-        enum_type->data.enumeration.is_invalid = true;
+    AstNode *decl_node = enum_type->data.enumeration.decl_node;
+    assert(decl_node->type == NodeTypeContainerDecl);
+
+    if (enum_type->data.enumeration.resolve_loop_flag) {
+        if (enum_type->data.enumeration.resolve_status != ResolveStatusInvalid) {
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
+            add_node_error(g, decl_node,
+                buf_sprintf("enum '%s' depends on itself",
+                    buf_ptr(&enum_type->name)));
+        }
         return ErrorSemanticAnalyzeFail;
     }
 
-    enum_type->data.enumeration.zero_bits_loop_flag = true;
-
-    AstNode *decl_node = enum_type->data.enumeration.decl_node;
-    assert(decl_node->type == NodeTypeContainerDecl);
+    enum_type->data.enumeration.resolve_loop_flag = true;
 
     assert(!enum_type->data.enumeration.fields);
     uint32_t field_count = (uint32_t)decl_node->data.container_decl.fields.length;
@@ -1951,9 +2176,7 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
 
         enum_type->data.enumeration.src_field_count = field_count;
         enum_type->data.enumeration.fields = nullptr;
-        enum_type->data.enumeration.is_invalid = true;
-        enum_type->data.enumeration.zero_bits_loop_flag = false;
-        enum_type->data.enumeration.zero_bits_known = true;
+        enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
         return ErrorSemanticAnalyzeFail;
     }
 
@@ -1982,14 +2205,14 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
     if (decl_node->data.container_decl.init_arg_expr != nullptr) {
         ZigType *wanted_tag_int_type = analyze_type_expr(g, scope, decl_node->data.container_decl.init_arg_expr);
         if (type_is_invalid(wanted_tag_int_type)) {
-            enum_type->data.enumeration.is_invalid = true;
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
         } else if (wanted_tag_int_type->id != ZigTypeIdInt) {
-            enum_type->data.enumeration.is_invalid = true;
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
             add_node_error(g, decl_node->data.container_decl.init_arg_expr,
                 buf_sprintf("expected integer, found '%s'", buf_ptr(&wanted_tag_int_type->name)));
         } else if (enum_type->data.enumeration.layout == ContainerLayoutExtern &&
                    !type_is_valid_extern_enum_tag(g, wanted_tag_int_type)) {
-            enum_type->data.enumeration.is_invalid = true;
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
             ErrorMsg *msg = add_node_error(g, decl_node->data.container_decl.init_arg_expr,
                 buf_sprintf("'%s' is not a valid tag type for an extern enum",
                             buf_ptr(&wanted_tag_int_type->name)));
@@ -2022,6 +2245,11 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
                 buf_sprintf("structs and unions, not enums, support field types"));
             add_error_note(g, msg, decl_node,
                     buf_sprintf("consider 'union(enum)' here"));
+        } else if (field_node->data.struct_field.align_expr != nullptr) {
+            ErrorMsg *msg = add_node_error(g, field_node->data.struct_field.align_expr,
+                buf_sprintf("structs and unions, not enums, support field alignment"));
+            add_error_note(g, msg, decl_node,
+                    buf_sprintf("consider 'union(enum)' here"));
         }
 
         auto field_entry = enum_type->data.enumeration.fields_by_name.put_unique(type_enum_field->name, type_enum_field);
@@ -2029,7 +2257,7 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
             ErrorMsg *msg = add_node_error(g, field_node,
                 buf_sprintf("duplicate enum field: '%s'", buf_ptr(type_enum_field->name)));
             add_error_note(g, msg, field_entry->value->decl_node, buf_sprintf("other field here"));
-            enum_type->data.enumeration.is_invalid = true;
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
             continue;
         }
 
@@ -2037,9 +2265,10 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
 
         if (tag_value != nullptr) {
             // A user-specified value is available
-            ConstExprValue *result = analyze_const_value(g, scope, tag_value, tag_int_type, nullptr);
+            ConstExprValue *result = analyze_const_value(g, scope, tag_value, tag_int_type,
+                    nullptr, UndefBad);
             if (type_is_invalid(result->type)) {
-                enum_type->data.enumeration.is_invalid = true;
+                enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
                 continue;
             }
 
@@ -2060,7 +2289,7 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
             if (!bigint_fits_in_bits(&type_enum_field->value,
                                      tag_int_type->size_in_bits,
                                      tag_int_type->data.integral.is_signed)) {
-                enum_type->data.enumeration.is_invalid = true;
+                enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
 
                 Buf *val_buf = buf_alloc();
                 bigint_append_buf(val_buf, &type_enum_field->value, 10);
@@ -2075,7 +2304,7 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
         // Make sure the value is unique
         auto entry = occupied_tag_values.put_unique(type_enum_field->value, field_node);
         if (entry != nullptr) {
-            enum_type->data.enumeration.is_invalid = true;
+            enum_type->data.enumeration.resolve_status = ResolveStatusInvalid;
 
             Buf *val_buf = buf_alloc();
             bigint_append_buf(val_buf, &type_enum_field->value, 10);
@@ -2089,13 +2318,12 @@ static Error resolve_enum_zero_bits(CodeGen *g, ZigType *enum_type) {
         last_enum_field = type_enum_field;
     }
 
-    enum_type->data.enumeration.zero_bits_loop_flag = false;
-    enum_type->data.enumeration.zero_bits_known = true;
-    enum_type->data.enumeration.complete = true;
-
-    if (enum_type->data.enumeration.is_invalid)
+    if (enum_type->data.enumeration.resolve_status == ResolveStatusInvalid)
         return ErrorSemanticAnalyzeFail;
 
+    enum_type->data.enumeration.resolve_loop_flag = false;
+    enum_type->data.enumeration.resolve_status = ResolveStatusSizeKnown;
+
     return ErrorNone;
 }
 
@@ -2112,16 +2340,17 @@ static Error resolve_struct_zero_bits(CodeGen *g, ZigType *struct_type) {
     AstNode *decl_node = struct_type->data.structure.decl_node;
     assert(decl_node->type == NodeTypeContainerDecl);
 
-    if (struct_type->data.structure.resolve_loop_flag) {
-        // TODO This is a problem. I believe it can be solved with lazy values.
-        struct_type->size_in_bits = SIZE_MAX;
-        struct_type->abi_size = SIZE_MAX;
-        struct_type->data.structure.resolve_status = ResolveStatusZeroBitsKnown;
-        struct_type->data.structure.resolve_loop_flag = false;
-        return ErrorNone;
+    if (struct_type->data.structure.resolve_loop_flag_zero_bits) {
+        if (struct_type->data.structure.resolve_status != ResolveStatusInvalid) {
+            struct_type->data.structure.resolve_status = ResolveStatusInvalid;
+            add_node_error(g, decl_node,
+                buf_sprintf("struct '%s' depends on itself",
+                    buf_ptr(&struct_type->name)));
+        }
+        return ErrorSemanticAnalyzeFail;
     }
 
-    struct_type->data.structure.resolve_loop_flag = true;
+    struct_type->data.structure.resolve_loop_flag_zero_bits = true;
 
     assert(!struct_type->data.structure.fields);
     size_t field_count = decl_node->data.container_decl.fields.length;
@@ -2153,58 +2382,60 @@ static Error resolve_struct_zero_bits(CodeGen *g, ZigType *struct_type) {
             return ErrorSemanticAnalyzeFail;
         }
 
-        ZigType *field_type = analyze_type_expr(g, scope, field_node->data.struct_field.type);
-        type_struct_field->type_entry = field_type;
-        if (type_is_invalid(field_type)) {
+        ConstExprValue *field_type_val = analyze_const_value(g, scope,
+                field_node->data.struct_field.type, g->builtin_types.entry_type, nullptr, LazyOkNoUndef);
+        if (type_is_invalid(field_type_val->type)) {
             struct_type->data.structure.resolve_status = ResolveStatusInvalid;
             return ErrorSemanticAnalyzeFail;
         }
+        assert(field_type_val->special != ConstValSpecialRuntime);
+        type_struct_field->type_val = field_type_val;
         if (struct_type->data.structure.resolve_status == ResolveStatusInvalid)
             return ErrorSemanticAnalyzeFail;
 
-        if (struct_type->data.structure.layout == ContainerLayoutExtern &&
-            !type_allowed_in_extern(g, field_type))
-        {
-            add_node_error(g, field_node,
-                    buf_sprintf("extern structs cannot contain fields of type '%s'",
-                        buf_ptr(&field_type->name)));
+        bool field_is_opaque_type;
+        if ((err = type_val_resolve_is_opaque_type(g, field_type_val, &field_is_opaque_type))) {
             struct_type->data.structure.resolve_status = ResolveStatusInvalid;
             return ErrorSemanticAnalyzeFail;
-        } else if (struct_type->data.structure.layout == ContainerLayoutPacked) {
-            if ((err = emit_error_unless_type_allowed_in_packed_struct(g, field_type, field_node))) {
-                struct_type->data.structure.resolve_status = ResolveStatusInvalid;
-                return ErrorSemanticAnalyzeFail;
-            }
         }
-
-        type_struct_field->src_index = i;
-        type_struct_field->gen_index = SIZE_MAX;
-
-        if (field_type->id == ZigTypeIdOpaque) {
+        if (field_is_opaque_type) {
             add_node_error(g, field_node->data.struct_field.type,
                 buf_sprintf("opaque types have unknown size and therefore cannot be directly embedded in structs"));
             struct_type->data.structure.resolve_status = ResolveStatusInvalid;
             return ErrorSemanticAnalyzeFail;
         }
-        switch (type_requires_comptime(g, field_type)) {
+
+        type_struct_field->src_index = i;
+        type_struct_field->gen_index = SIZE_MAX;
+
+        switch (type_val_resolve_requires_comptime(g, field_type_val)) {
             case ReqCompTimeYes:
                 struct_type->data.structure.requires_comptime = true;
                 break;
             case ReqCompTimeInvalid:
+                if (g->trace_err != nullptr) {
+                    g->trace_err = add_error_note(g, g->trace_err, field_node,
+                        buf_create_from_str("while checking this field"));
+                }
                 struct_type->data.structure.resolve_status = ResolveStatusInvalid;
                 return ErrorSemanticAnalyzeFail;
             case ReqCompTimeNo:
                 break;
         }
 
-        if (!type_has_bits(field_type))
+        bool field_is_zero_bits;
+        if ((err = type_val_resolve_zero_bits(g, field_type_val, struct_type, nullptr, &field_is_zero_bits))) {
+            struct_type->data.structure.resolve_status = ResolveStatusInvalid;
+            return ErrorSemanticAnalyzeFail;
+        }
+        if (field_is_zero_bits)
             continue;
 
         type_struct_field->gen_index = gen_field_index;
         gen_field_index += 1;
     }
 
-    struct_type->data.structure.resolve_loop_flag = false;
+    struct_type->data.structure.resolve_loop_flag_zero_bits = false;
     struct_type->data.structure.gen_field_count = (uint32_t)gen_field_index;
     if (gen_field_index != 0) {
         struct_type->abi_size = SIZE_MAX;
@@ -2234,17 +2465,16 @@ static Error resolve_struct_alignment(CodeGen *g, ZigType *struct_type) {
 
     AstNode *decl_node = struct_type->data.structure.decl_node;
 
-    if (struct_type->data.structure.resolve_loop_flag) {
+    if (struct_type->data.structure.resolve_loop_flag_other) {
         if (struct_type->data.structure.resolve_status != ResolveStatusInvalid) {
             struct_type->data.structure.resolve_status = ResolveStatusInvalid;
-            ErrorMsg *msg = add_node_error(g, decl_node,
-                buf_sprintf("struct '%s' contains itself", buf_ptr(&struct_type->name)));
-            emit_error_notes_for_ref_stack(g, msg);
+            add_node_error(g, decl_node,
+                buf_sprintf("struct '%s' depends on itself", buf_ptr(&struct_type->name)));
         }
         return ErrorSemanticAnalyzeFail;
     }
 
-    struct_type->data.structure.resolve_loop_flag = true;
+    struct_type->data.structure.resolve_loop_flag_other = true;
     assert(decl_node->type == NodeTypeContainerDecl);
 
     size_t field_count = struct_type->data.structure.src_field_count;
@@ -2255,47 +2485,31 @@ static Error resolve_struct_alignment(CodeGen *g, ZigType *struct_type) {
         if (field->gen_index == SIZE_MAX)
             continue;
 
-        uint32_t this_field_align;
-
-        // TODO: Sets the field alignment in the type, but doesn't do anything
-        // to actually make that happen yet.
         AstNode *align_expr = field->decl_node->data.struct_field.align_expr;
         if (align_expr != nullptr) {
-            if (!analyze_const_align(g, &struct_type->data.structure.decls_scope->base, align_expr, &this_field_align)) {
-                field->type_entry = g->builtin_types.entry_invalid;
-            } else {
-                field->align = this_field_align;
+            if (!analyze_const_align(g, &struct_type->data.structure.decls_scope->base, align_expr,
+                        &field->align))
+            {
+                struct_type->data.structure.resolve_status = ResolveStatusInvalid;
+                return err;
             }
         } else if (packed) {
-            // TODO: https://github.com/ziglang/zig/issues/1512
-            // TODO: Validate requested alignment is possible, given packed,
-            // and given other field alignments.
-            this_field_align = 1;
-        // TODO If we have no type_entry for the field, we've already failed to
-        // compile the program correctly. This stage1 compiler needs a deeper
-        // reworking to make this correct, or we can ignore the problem
-        // and make sure it is fixed in stage2. This workaround is for when
-        // there is a false positive of a dependency loop, of alignment depending
-        // on itself. When this false positive happens we assume a pointer-aligned
-        // field, which is usually fine but could be incorrectly over-aligned or
-        // even under-aligned. See https://github.com/ziglang/zig/issues/1512
-        } else if (field->type_entry == nullptr) {
-            this_field_align = g->builtin_types.entry_usize->abi_align;
+            field->align = 1;
         } else {
-            if ((err = type_resolve(g, field->type_entry, ResolveStatusAlignmentKnown))) {
+            if ((err = type_val_resolve_abi_align(g, field->type_val, &field->align))) {
                 struct_type->data.structure.resolve_status = ResolveStatusInvalid;
-                return ErrorSemanticAnalyzeFail;
+                return err;
             }
-            this_field_align = field->type_entry->abi_align;
+            if (struct_type->data.structure.resolve_status == ResolveStatusInvalid)
+                return ErrorSemanticAnalyzeFail;
         }
 
-        // TODO: https://github.com/ziglang/zig/issues/1512
-        if (this_field_align > struct_type->abi_align) {
-            struct_type->abi_align = this_field_align;
+        if (field->align > struct_type->abi_align) {
+            struct_type->abi_align = field->align;
         }
     }
 
-    struct_type->data.structure.resolve_loop_flag = false;
+    struct_type->data.structure.resolve_loop_flag_other = false;
 
     if (struct_type->data.structure.resolve_status == ResolveStatusInvalid) {
         return ErrorSemanticAnalyzeFail;
@@ -2316,23 +2530,21 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
     if (union_type->data.unionation.resolve_status >= ResolveStatusZeroBitsKnown)
         return ErrorNone;
 
-    if (union_type->data.unionation.resolve_loop_flag) {
-        // If we get here it's due to recursion. From this we conclude that the struct is
-        // not zero bits.
-        // TODO actually it could still be zero bits. Here we should continue analyzing
-        // the union from the next field index.
-        union_type->data.unionation.resolve_status = ResolveStatusZeroBitsKnown;
-        union_type->data.unionation.resolve_loop_flag = false;
-        union_type->abi_size = SIZE_MAX;
-        union_type->size_in_bits = SIZE_MAX;
-        return ErrorNone;
-    }
-
-    union_type->data.unionation.resolve_loop_flag = true;
-
     AstNode *decl_node = union_type->data.unionation.decl_node;
     assert(decl_node->type == NodeTypeContainerDecl);
 
+    if (union_type->data.unionation.resolve_loop_flag_zero_bits) {
+        if (union_type->data.unionation.resolve_status != ResolveStatusInvalid) {
+            union_type->data.unionation.resolve_status = ResolveStatusInvalid;
+            add_node_error(g, decl_node,
+                buf_sprintf("union '%s' depends on itself",
+                    buf_ptr(&union_type->name)));
+        }
+        return ErrorSemanticAnalyzeFail;
+    }
+
+    union_type->data.unionation.resolve_loop_flag_zero_bits = true;
+
     assert(union_type->data.unionation.fields == nullptr);
     uint32_t field_count = (uint32_t)decl_node->data.container_decl.fields.length;
     if (field_count == 0) {
@@ -2392,14 +2604,13 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
         tag_type->size_in_bits = tag_int_type->size_in_bits;
 
         tag_type->data.enumeration.tag_int_type = tag_int_type;
-        tag_type->data.enumeration.zero_bits_known = true;
+        tag_type->data.enumeration.resolve_status = ResolveStatusSizeKnown;
         tag_type->data.enumeration.decl_node = decl_node;
         tag_type->data.enumeration.layout = ContainerLayoutAuto;
         tag_type->data.enumeration.src_field_count = field_count;
         tag_type->data.enumeration.fields = allocate<TypeEnumField>(field_count);
         tag_type->data.enumeration.fields_by_name.init(field_count);
         tag_type->data.enumeration.decls_scope = union_type->data.unionation.decls_scope;
-        tag_type->data.enumeration.complete = true;
     } else if (enum_type_node != nullptr) {
         ZigType *enum_type = analyze_type_expr(g, scope, enum_type_node);
         if (type_is_invalid(enum_type)) {
@@ -2441,49 +2652,68 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
             return ErrorSemanticAnalyzeFail;
         }
 
-        ZigType *field_type;
+        bool field_is_zero_bits;
         if (field_node->data.struct_field.type == nullptr) {
-            if (decl_node->data.container_decl.auto_enum || decl_node->data.container_decl.init_arg_expr != nullptr) {
-                field_type = g->builtin_types.entry_void;
+            if (decl_node->data.container_decl.auto_enum ||
+                decl_node->data.container_decl.init_arg_expr != nullptr)
+            {
+                union_field->type_entry = g->builtin_types.entry_void;
+                field_is_zero_bits = true;
             } else {
                 add_node_error(g, field_node, buf_sprintf("union field missing type"));
                 union_type->data.unionation.resolve_status = ResolveStatusInvalid;
                 return ErrorSemanticAnalyzeFail;
             }
         } else {
-            field_type = analyze_type_expr(g, scope, field_node->data.struct_field.type);
-            if ((err = type_resolve(g, field_type, ResolveStatusAlignmentKnown))) {
+            ConstExprValue *field_type_val = analyze_const_value(g, scope,
+                    field_node->data.struct_field.type, g->builtin_types.entry_type, nullptr, LazyOkNoUndef);
+            if (type_is_invalid(field_type_val->type)) {
                 union_type->data.unionation.resolve_status = ResolveStatusInvalid;
                 return ErrorSemanticAnalyzeFail;
             }
+            assert(field_type_val->special != ConstValSpecialRuntime);
+            union_field->type_val = field_type_val;
             if (union_type->data.unionation.resolve_status == ResolveStatusInvalid)
                 return ErrorSemanticAnalyzeFail;
-        }
-        union_field->type_entry = field_type;
 
-        if (field_type->id == ZigTypeIdOpaque) {
-            add_node_error(g, field_node->data.struct_field.type,
-                buf_sprintf("opaque types have unknown size and therefore cannot be directly embedded in unions"));
-            union_type->data.unionation.resolve_status = ResolveStatusInvalid;
-            return ErrorSemanticAnalyzeFail;
-        }
+            bool field_is_opaque_type;
+            if ((err = type_val_resolve_is_opaque_type(g, field_type_val, &field_is_opaque_type))) {
+                union_type->data.unionation.resolve_status = ResolveStatusInvalid;
+                return ErrorSemanticAnalyzeFail;
+            }
+            if (field_is_opaque_type) {
+                add_node_error(g, field_node->data.struct_field.type,
+                    buf_create_from_str(
+                        "opaque types have unknown size and therefore cannot be directly embedded in unions"));
+                union_type->data.unionation.resolve_status = ResolveStatusInvalid;
+                return ErrorSemanticAnalyzeFail;
+            }
 
-        switch (type_requires_comptime(g, field_type)) {
-            case ReqCompTimeInvalid:
+            switch (type_val_resolve_requires_comptime(g, field_type_val)) {
+                case ReqCompTimeInvalid:
+                    if (g->trace_err != nullptr) {
+                        g->trace_err = add_error_note(g, g->trace_err, field_node,
+                            buf_create_from_str("while checking this field"));
+                    }
+                    union_type->data.unionation.resolve_status = ResolveStatusInvalid;
+                    return ErrorSemanticAnalyzeFail;
+                case ReqCompTimeYes:
+                    union_type->data.unionation.requires_comptime = true;
+                    break;
+                case ReqCompTimeNo:
+                    break;
+            }
+
+            if ((err = type_val_resolve_zero_bits(g, field_type_val, union_type, nullptr, &field_is_zero_bits))) {
                 union_type->data.unionation.resolve_status = ResolveStatusInvalid;
                 return ErrorSemanticAnalyzeFail;
-            case ReqCompTimeYes:
-                union_type->data.unionation.requires_comptime = true;
-                break;
-            case ReqCompTimeNo:
-                break;
+            }
         }
 
         if (field_node->data.struct_field.value != nullptr && !decl_node->data.container_decl.auto_enum) {
             ErrorMsg *msg = add_node_error(g, field_node->data.struct_field.value,
-                    buf_sprintf("non-enum union field assignment"));
-            add_error_note(g, msg, decl_node,
-                    buf_sprintf("consider 'union(enum)' here"));
+                    buf_create_from_str("untagged union field assignment"));
+            add_error_note(g, msg, decl_node, buf_create_from_str("consider 'union(enum)' here"));
         }
 
         if (create_enum_type) {
@@ -2501,7 +2731,8 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
             // In a second pass we will fill in the unspecified ones.
             if (tag_value != nullptr) {
                 ZigType *tag_int_type = tag_type->data.enumeration.tag_int_type;
-                ConstExprValue *result = analyze_const_value(g, scope, tag_value, tag_int_type, nullptr);
+                ConstExprValue *result = analyze_const_value(g, scope, tag_value, tag_int_type,
+                        nullptr, UndefBad);
                 if (type_is_invalid(result->type)) {
                     union_type->data.unionation.resolve_status = ResolveStatusInvalid;
                     return ErrorSemanticAnalyzeFail;
@@ -2542,7 +2773,7 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
         }
         assert(union_field->enum_field != nullptr);
 
-        if (!type_has_bits(field_type))
+        if (field_is_zero_bits)
             continue;
 
         union_field->gen_index = gen_field_index;
@@ -2619,7 +2850,7 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
         return ErrorSemanticAnalyzeFail;
     }
 
-    union_type->data.unionation.resolve_loop_flag = false;
+    union_type->data.unionation.resolve_loop_flag_zero_bits = false;
 
     union_type->data.unionation.gen_field_count = gen_field_index;
     bool zero_bits = gen_field_index == 0 && (field_count < 2 || !src_have_tag);
@@ -2676,6 +2907,8 @@ ZigFn *create_fn(CodeGen *g, AstNode *proto_node) {
     fn_entry->body_node = (proto_node->data.fn_proto.fn_def_node == nullptr) ? nullptr :
         proto_node->data.fn_proto.fn_def_node->data.fn_def.body;
 
+    fn_entry->analyzed_executable.source_node = fn_entry->body_node;
+
     return fn_entry;
 }
 
@@ -2702,7 +2935,7 @@ void typecheck_panic_fn(CodeGen *g, TldFn *tld_fn, ZigFn *panic_fn) {
     fake_decl->data.symbol_expr.symbol = tld_fn->base.name;
 
     // call this for the side effects of casting to panic_fn_type
-    analyze_const_value(g, tld_fn->base.parent_scope, fake_decl, panic_fn_type, nullptr);
+    analyze_const_value(g, tld_fn->base.parent_scope, fake_decl, panic_fn_type, nullptr, UndefBad);
 }
 
 ZigType *get_test_fn_type(CodeGen *g) {
@@ -2848,7 +3081,8 @@ static void resolve_decl_fn(CodeGen *g, TldFn *tld_fn) {
 static void resolve_decl_comptime(CodeGen *g, TldCompTime *tld_comptime) {
     assert(tld_comptime->base.source_node->type == NodeTypeCompTime);
     AstNode *expr_node = tld_comptime->base.source_node->data.comptime_expr.expr;
-    analyze_const_value(g, tld_comptime->base.parent_scope, expr_node, g->builtin_types.entry_void, nullptr);
+    analyze_const_value(g, tld_comptime->base.parent_scope, expr_node, g->builtin_types.entry_void,
+            nullptr, UndefBad);
 }
 
 static void add_top_level_decl(CodeGen *g, ScopeDecls *decls_scope, Tld *tld) {
@@ -2943,7 +3177,7 @@ void init_tld(Tld *tld, TldId id, Buf *name, VisibMod visib_mod, AstNode *source
 
 void update_compile_var(CodeGen *g, Buf *name, ConstExprValue *value) {
     Tld *tld = get_container_scope(g->compile_var_import)->decl_table.get(name);
-    resolve_top_level_decl(g, tld, tld->source_node);
+    resolve_top_level_decl(g, tld, tld->source_node, false);
     assert(tld->id == TldIdVar);
     TldVar *tld_var = (TldVar *)tld;
     tld_var->var->const_value = value;
@@ -3185,7 +3419,7 @@ ZigVar *add_variable(CodeGen *g, AstNode *source_node, Scope *parent_scope, Buf
     return variable_entry;
 }
 
-static void resolve_decl_var(CodeGen *g, TldVar *tld_var) {
+static void resolve_decl_var(CodeGen *g, TldVar *tld_var, bool allow_lazy) {
     AstNode *source_node = tld_var->base.source_node;
     AstNodeVariableDeclaration *var_decl = &source_node->data.variable_declaration;
 
@@ -3197,9 +3431,8 @@ static void resolve_decl_var(CodeGen *g, TldVar *tld_var) {
     ZigType *explicit_type = nullptr;
     if (var_decl->type) {
         if (tld_var->analyzing_type) {
-            ErrorMsg *msg = add_node_error(g, var_decl->type,
+            add_node_error(g, var_decl->type,
                 buf_sprintf("type of '%s' depends on itself", buf_ptr(tld_var->base.name)));
-            emit_error_notes_for_ref_stack(g, msg);
             explicit_type = g->builtin_types.entry_invalid;
         } else {
             tld_var->analyzing_type = true;
@@ -3217,7 +3450,8 @@ static void resolve_decl_var(CodeGen *g, TldVar *tld_var) {
     if (explicit_type && explicit_type->id == ZigTypeIdInvalid) {
         implicit_type = explicit_type;
     } else if (var_decl->expr) {
-        init_value = analyze_const_value(g, tld_var->base.parent_scope, var_decl->expr, explicit_type, var_decl->symbol);
+        init_value = analyze_const_value(g, tld_var->base.parent_scope, var_decl->expr, explicit_type,
+                var_decl->symbol, allow_lazy ? LazyOk : UndefOk);
         assert(init_value);
         implicit_type = init_value->type;
 
@@ -3372,7 +3606,8 @@ static void preview_use_decl(CodeGen *g, TldUsingNamespace *using_namespace, Sco
     using_namespace->base.resolution = TldResolutionResolving;
     assert(using_namespace->base.source_node->type == NodeTypeUsingNamespace);
     ConstExprValue *result = analyze_const_value(g, &dest_decls_scope->base,
-        using_namespace->base.source_node->data.using_namespace.expr, g->builtin_types.entry_type, nullptr);
+        using_namespace->base.source_node->data.using_namespace.expr, g->builtin_types.entry_type,
+        nullptr, UndefBad);
     using_namespace->using_namespace_value = result;
 
     if (type_is_invalid(result->type)) {
@@ -3392,51 +3627,61 @@ static void preview_use_decl(CodeGen *g, TldUsingNamespace *using_namespace, Sco
     }
 }
 
-void resolve_top_level_decl(CodeGen *g, Tld *tld, AstNode *source_node) {
-    if (tld->resolution != TldResolutionUnresolved)
+void resolve_top_level_decl(CodeGen *g, Tld *tld, AstNode *source_node, bool allow_lazy) {
+    bool want_resolve_lazy = tld->resolution == TldResolutionOkLazy && !allow_lazy;
+    if (tld->resolution != TldResolutionUnresolved && !want_resolve_lazy)
         return;
 
-    assert(tld->resolution != TldResolutionResolving);
     tld->resolution = TldResolutionResolving;
-    g->tld_ref_source_node_stack.append(source_node);
 
     switch (tld->id) {
-        case TldIdVar:
-            {
-                TldVar *tld_var = (TldVar *)tld;
-                resolve_decl_var(g, tld_var);
-                break;
-            }
-        case TldIdFn:
-            {
-                TldFn *tld_fn = (TldFn *)tld;
-                resolve_decl_fn(g, tld_fn);
-                break;
-            }
-        case TldIdContainer:
-            {
-                TldContainer *tld_container = (TldContainer *)tld;
-                resolve_decl_container(g, tld_container);
-                break;
-            }
-        case TldIdCompTime:
-            {
-                TldCompTime *tld_comptime = (TldCompTime *)tld;
-                resolve_decl_comptime(g, tld_comptime);
-                break;
+        case TldIdVar: {
+            TldVar *tld_var = (TldVar *)tld;
+            if (want_resolve_lazy) {
+                ir_resolve_lazy(g, source_node, tld_var->var->const_value);
+            } else {
+                resolve_decl_var(g, tld_var, allow_lazy);
             }
+            tld->resolution = allow_lazy ? TldResolutionOkLazy : TldResolutionOk;
+            break;
+        }
+        case TldIdFn: {
+            TldFn *tld_fn = (TldFn *)tld;
+            resolve_decl_fn(g, tld_fn);
+
+            tld->resolution = TldResolutionOk;
+            break;
+        }
+        case TldIdContainer: {
+            TldContainer *tld_container = (TldContainer *)tld;
+            resolve_decl_container(g, tld_container);
+
+            tld->resolution = TldResolutionOk;
+            break;
+        }
+        case TldIdCompTime: {
+            TldCompTime *tld_comptime = (TldCompTime *)tld;
+            resolve_decl_comptime(g, tld_comptime);
+
+            tld->resolution = TldResolutionOk;
+            break;
+        }
         case TldIdUsingNamespace: {
             TldUsingNamespace *tld_using_namespace = (TldUsingNamespace *)tld;
             assert(tld_using_namespace->base.parent_scope->id == ScopeIdDecls);
             ScopeDecls *dest_decls_scope = (ScopeDecls *)tld_using_namespace->base.parent_scope;
             preview_use_decl(g, tld_using_namespace, dest_decls_scope);
             resolve_use_decl(g, tld_using_namespace, dest_decls_scope);
+
+            tld->resolution = TldResolutionOk;
             break;
         }
     }
 
-    tld->resolution = TldResolutionOk;
-    g->tld_ref_source_node_stack.pop();
+    if (g->trace_err != nullptr && source_node != nullptr && !source_node->already_traced_this_node) {
+        g->trace_err = add_error_note(g, g->trace_err, source_node, buf_create_from_str("referenced here"));
+        source_node->already_traced_this_node = true;
+    }
 }
 
 Tld *find_container_decl(CodeGen *g, ScopeDecls *decls_scope, Buf *name) {
@@ -3562,7 +3807,7 @@ TypeUnionField *find_union_field_by_tag(ZigType *type_entry, const BigInt *tag)
 }
 
 TypeEnumField *find_enum_field_by_tag(ZigType *enum_type, const BigInt *tag) {
-    assert(enum_type->data.enumeration.zero_bits_known);
+    assert(type_is_resolved(enum_type, ResolveStatusZeroBitsKnown));
     for (uint32_t i = 0; i < enum_type->data.enumeration.src_field_count; i += 1) {
         TypeEnumField *field = &enum_type->data.enumeration.fields[i];
         if (bigint_cmp(&field->value, tag) == CmpEQ) {
@@ -3631,43 +3876,6 @@ ZigType *container_ref_type(ZigType *type_entry) {
         type_entry->data.pointer.child_type : type_entry;
 }
 
-Error resolve_container_type(CodeGen *g, ZigType *type_entry) {
-    switch (type_entry->id) {
-        case ZigTypeIdStruct:
-            return resolve_struct_type(g, type_entry);
-        case ZigTypeIdEnum:
-            return resolve_enum_zero_bits(g, type_entry);
-        case ZigTypeIdUnion:
-            return resolve_union_type(g, type_entry);
-        case ZigTypeIdPointer:
-        case ZigTypeIdMetaType:
-        case ZigTypeIdVoid:
-        case ZigTypeIdBool:
-        case ZigTypeIdUnreachable:
-        case ZigTypeIdInt:
-        case ZigTypeIdFloat:
-        case ZigTypeIdArray:
-        case ZigTypeIdComptimeFloat:
-        case ZigTypeIdComptimeInt:
-        case ZigTypeIdEnumLiteral:
-        case ZigTypeIdUndefined:
-        case ZigTypeIdNull:
-        case ZigTypeIdOptional:
-        case ZigTypeIdErrorUnion:
-        case ZigTypeIdErrorSet:
-        case ZigTypeIdFn:
-        case ZigTypeIdBoundFn:
-        case ZigTypeIdInvalid:
-        case ZigTypeIdArgTuple:
-        case ZigTypeIdOpaque:
-        case ZigTypeIdVector:
-        case ZigTypeIdFnFrame:
-        case ZigTypeIdAnyFrame:
-            zig_unreachable();
-    }
-    zig_unreachable();
-}
-
 ZigType *get_src_ptr_type(ZigType *type) {
     if (type->id == ZigTypeIdPointer) return type;
     if (type->id == ZigTypeIdFn) return type;
@@ -3803,6 +4011,13 @@ static void resolve_async_fn_frame(CodeGen *g, ZigFn *fn) {
     ZigType *frame_type = get_fn_frame_type(g, fn);
     Error err;
     if ((err = type_resolve(g, frame_type, ResolveStatusSizeKnown))) {
+        if (g->trace_err != nullptr && frame_type->data.frame.resolve_loop_src_node != nullptr &&
+            !frame_type->data.frame.reported_loop_err)
+        {
+            frame_type->data.frame.reported_loop_err = true;
+            g->trace_err = add_error_note(g, g->trace_err, frame_type->data.frame.resolve_loop_src_node,
+                buf_sprintf("when analyzing type '%s' here", buf_ptr(&frame_type->name)));
+        }
         fn->anal_state = FnAnalStateInvalid;
         return;
     }
@@ -3918,7 +4133,7 @@ static void analyze_fn_ir(CodeGen *g, ZigFn *fn, AstNode *return_type_node) {
             &fn->analyzed_executable, fn_type_id->return_type, return_type_node);
     fn->src_implicit_return_type = block_return_type;
 
-    if (type_is_invalid(block_return_type) || fn->analyzed_executable.invalid) {
+    if (type_is_invalid(block_return_type) || fn->analyzed_executable.first_err_trace_msg != nullptr) {
         assert(g->errors.length > 0);
         fn->anal_state = FnAnalStateInvalid;
         return;
@@ -4002,7 +4217,7 @@ static void analyze_fn_body(CodeGen *g, ZigFn *fn_table_entry) {
     assert(!fn_type->data.fn.is_generic);
 
     ir_gen_fn(g, fn_table_entry);
-    if (fn_table_entry->ir_executable.invalid) {
+    if (fn_table_entry->ir_executable.first_err_trace_msg != nullptr) {
         fn_table_entry->anal_state = FnAnalStateInvalid;
         return;
     }
@@ -4140,12 +4355,14 @@ void semantic_analyze(CodeGen *g) {
     {
         for (; g->resolve_queue_index < g->resolve_queue.length; g->resolve_queue_index += 1) {
             Tld *tld = g->resolve_queue.at(g->resolve_queue_index);
+            g->trace_err = nullptr;
             AstNode *source_node = nullptr;
-            resolve_top_level_decl(g, tld, source_node);
+            resolve_top_level_decl(g, tld, source_node, false);
         }
 
         for (; g->fn_defs_index < g->fn_defs.length; g->fn_defs_index += 1) {
             ZigFn *fn_entry = g->fn_defs.at(g->fn_defs_index);
+            g->trace_err = nullptr;
             analyze_fn_body(g, fn_entry);
         }
     }
@@ -4157,6 +4374,7 @@ void semantic_analyze(CodeGen *g) {
     // second pass over functions for detecting async
     for (g->fn_defs_index = 0; g->fn_defs_index < g->fn_defs.length; g->fn_defs_index += 1) {
         ZigFn *fn = g->fn_defs.at(g->fn_defs_index);
+        g->trace_err = nullptr;
         analyze_fn_async(g, fn, true);
         if (fn_is_async(fn) && fn->non_async_node != nullptr) {
             ErrorMsg *msg = add_node_error(g, fn->proto_node,
@@ -4802,7 +5020,10 @@ OnePossibleValue type_has_one_possible_value(CodeGen *g, ZigType *type_entry) {
         case ZigTypeIdStruct:
             for (size_t i = 0; i < type_entry->data.structure.src_field_count; i += 1) {
                 TypeStructField *field = &type_entry->data.structure.fields[i];
-                switch (type_has_one_possible_value(g, field->type_entry)) {
+                OnePossibleValue opv = (field->type_entry != nullptr) ?
+                    type_has_one_possible_value(g, field->type_entry) :
+                    type_val_resolve_has_one_possible_value(g, field->type_val);
+                switch (opv) {
                     case OnePossibleValueInvalid:
                         return OnePossibleValueInvalid;
                     case OnePossibleValueNo:
@@ -4828,18 +5049,19 @@ OnePossibleValue type_has_one_possible_value(CodeGen *g, ZigType *type_entry) {
         case ZigTypeIdUnion:
             if (type_entry->data.unionation.src_field_count > 1)
                 return OnePossibleValueNo;
-            return type_has_one_possible_value(g, type_entry->data.unionation.fields[0].type_entry);
+            TypeUnionField *only_field = &type_entry->data.unionation.fields[0];
+            if (only_field->type_entry != nullptr) {
+                return type_has_one_possible_value(g, only_field->type_entry);
+            }
+            return type_val_resolve_has_one_possible_value(g, only_field->type_val);
     }
     zig_unreachable();
 }
 
-ReqCompTime type_requires_comptime(CodeGen *g, ZigType *type_entry) {
+ReqCompTime type_requires_comptime(CodeGen *g, ZigType *ty) {
     Error err;
-    if ((err = type_resolve(g, type_entry, ResolveStatusZeroBitsKnown)))
-        return ReqCompTimeInvalid;
-    switch (type_entry->id) {
+    switch (ty->id) {
         case ZigTypeIdInvalid:
-        case ZigTypeIdOpaque:
             zig_unreachable();
         case ZigTypeIdComptimeFloat:
         case ZigTypeIdComptimeInt:
@@ -4851,23 +5073,36 @@ ReqCompTime type_requires_comptime(CodeGen *g, ZigType *type_entry) {
         case ZigTypeIdArgTuple:
             return ReqCompTimeYes;
         case ZigTypeIdArray:
-            return type_requires_comptime(g, type_entry->data.array.child_type);
+            return type_requires_comptime(g, ty->data.array.child_type);
         case ZigTypeIdStruct:
-            return type_entry->data.structure.requires_comptime ? ReqCompTimeYes : ReqCompTimeNo;
+            if (ty->data.structure.resolve_loop_flag_zero_bits) {
+                // Does a struct which contains a pointer field to itself require comptime? No.
+                return ReqCompTimeNo;
+            }
+            if ((err = type_resolve(g, ty, ResolveStatusZeroBitsKnown)))
+                return ReqCompTimeInvalid;
+            return ty->data.structure.requires_comptime ? ReqCompTimeYes : ReqCompTimeNo;
         case ZigTypeIdUnion:
-            return type_entry->data.unionation.requires_comptime ? ReqCompTimeYes : ReqCompTimeNo;
+            if (ty->data.unionation.resolve_loop_flag_zero_bits) {
+                // Does a union which contains a pointer field to itself require comptime? No.
+                return ReqCompTimeNo;
+            }
+            if ((err = type_resolve(g, ty, ResolveStatusZeroBitsKnown)))
+                return ReqCompTimeInvalid;
+            return ty->data.unionation.requires_comptime ? ReqCompTimeYes : ReqCompTimeNo;
         case ZigTypeIdOptional:
-            return type_requires_comptime(g, type_entry->data.maybe.child_type);
+            return type_requires_comptime(g, ty->data.maybe.child_type);
         case ZigTypeIdErrorUnion:
-            return type_requires_comptime(g, type_entry->data.error_union.payload_type);
+            return type_requires_comptime(g, ty->data.error_union.payload_type);
         case ZigTypeIdPointer:
-            if (type_entry->data.pointer.child_type->id == ZigTypeIdOpaque) {
+            if (ty->data.pointer.child_type->id == ZigTypeIdOpaque) {
                 return ReqCompTimeNo;
             } else {
-                return type_requires_comptime(g, type_entry->data.pointer.child_type);
+                return type_requires_comptime(g, ty->data.pointer.child_type);
             }
         case ZigTypeIdFn:
-            return type_entry->data.fn.is_generic ? ReqCompTimeYes : ReqCompTimeNo;
+            return ty->data.fn.is_generic ? ReqCompTimeYes : ReqCompTimeNo;
+        case ZigTypeIdOpaque:
         case ZigTypeIdEnum:
         case ZigTypeIdErrorSet:
         case ZigTypeIdBool:
@@ -5155,34 +5390,6 @@ ConstExprValue *create_const_arg_tuple(CodeGen *g, size_t arg_index_start, size_
 }
 
 
-void init_const_undefined(CodeGen *g, ConstExprValue *const_val) {
-    Error err;
-    ZigType *wanted_type = const_val->type;
-    if (wanted_type->id == ZigTypeIdArray) {
-        const_val->special = ConstValSpecialStatic;
-        const_val->data.x_array.special = ConstArraySpecialUndef;
-    } else if (wanted_type->id == ZigTypeIdStruct) {
-        if ((err = ensure_complete_type(g, wanted_type))) {
-            return;
-        }
-
-        const_val->special = ConstValSpecialStatic;
-        size_t field_count = wanted_type->data.structure.src_field_count;
-        const_val->data.x_struct.fields = create_const_vals(field_count);
-        for (size_t i = 0; i < field_count; i += 1) {
-            ConstExprValue *field_val = &const_val->data.x_struct.fields[i];
-            field_val->type = wanted_type->data.structure.fields[i].type_entry;
-            assert(field_val->type);
-            init_const_undefined(g, field_val);
-            field_val->parent.id = ConstParentIdStruct;
-            field_val->parent.data.p_struct.struct_val = const_val;
-            field_val->parent.data.p_struct.field_index = i;
-        }
-    } else {
-        const_val->special = ConstValSpecialUndef;
-    }
-}
-
 ConstExprValue *create_const_vals(size_t count) {
     ConstGlobalRefs *global_refs = allocate<ConstGlobalRefs>(count);
     ConstExprValue *vals = allocate<ConstExprValue>(count);
@@ -5192,10 +5399,6 @@ ConstExprValue *create_const_vals(size_t count) {
     return vals;
 }
 
-Error ensure_complete_type(CodeGen *g, ZigType *type_entry) {
-    return type_resolve(g, type_entry, ResolveStatusSizeKnown);
-}
-
 static ZigType *get_async_fn_type(CodeGen *g, ZigType *orig_fn_type) {
     if (orig_fn_type->data.fn.fn_type_id.cc == CallingConventionAsync)
         return orig_fn_type;
@@ -5209,27 +5412,6 @@ static ZigType *get_async_fn_type(CodeGen *g, ZigType *orig_fn_type) {
     return fn_type;
 }
 
-static void emit_error_notes_for_type_loop(CodeGen *g, ErrorMsg *msg, ZigType *stop_type,
-        ZigType *ty, AstNode *src_node)
-{
-    ErrorMsg *note = add_error_note(g, msg, src_node,
-        buf_sprintf("when analyzing type '%s' here", buf_ptr(&ty->name)));
-    if (ty == stop_type)
-        return;
-    switch (ty->id) {
-        case ZigTypeIdFnFrame: {
-            ty->data.frame.reported_loop_err = true;
-            ZigType *depending_type = ty->data.frame.resolve_loop_type;
-            if (depending_type == nullptr)
-                return;
-            emit_error_notes_for_type_loop(g, note, stop_type,
-                depending_type, ty->data.frame.resolve_loop_src_node);
-        }
-        default:
-            return;
-    }
-}
-
 static Error resolve_async_frame(CodeGen *g, ZigType *frame_type) {
     Error err;
 
@@ -5241,14 +5423,8 @@ static Error resolve_async_frame(CodeGen *g, ZigType *frame_type) {
 
     if (frame_type->data.frame.resolve_loop_type != nullptr) {
         if (!frame_type->data.frame.reported_loop_err) {
-            frame_type->data.frame.reported_loop_err = true;
-            ErrorMsg *msg = add_node_error(g, fn->proto_node,
+            add_node_error(g, fn->proto_node,
                     buf_sprintf("'%s' depends on itself", buf_ptr(&frame_type->name)));
-            emit_error_notes_for_type_loop(g, msg,
-                    frame_type,
-                    frame_type->data.frame.resolve_loop_type,
-                    frame_type->data.frame.resolve_loop_src_node);
-            emit_error_notes_for_ref_stack(g, msg);
         }
         return ErrorSemanticAnalyzeFail;
     }
@@ -5264,11 +5440,9 @@ static Error resolve_async_frame(CodeGen *g, ZigType *frame_type) {
                 return ErrorSemanticAnalyzeFail;
             break;
         case FnAnalStateProbing: {
-            ErrorMsg *msg = add_node_error(g, fn->proto_node,
+            add_node_error(g, fn->proto_node,
                     buf_sprintf("cannot resolve '%s': function not fully analyzed yet",
                         buf_ptr(&frame_type->name)));
-            ir_add_analysis_trace(fn->ir_executable.analysis, msg,
-                    buf_sprintf("depends on its own frame here"));
             return ErrorSemanticAnalyzeFail;
         }
     }
@@ -5339,10 +5513,8 @@ static Error resolve_async_frame(CodeGen *g, ZigType *frame_type) {
         if (callee->anal_state == FnAnalStateProbing) {
             ErrorMsg *msg = add_node_error(g, fn->proto_node,
                 buf_sprintf("unable to determine async function frame of '%s'", buf_ptr(&fn->symbol_name)));
-            ErrorMsg *note = add_error_note(g, msg, call->base.source_node,
+            g->trace_err = add_error_note(g, msg, call->base.source_node,
                 buf_sprintf("analysis of function '%s' depends on the frame", buf_ptr(&callee->symbol_name)));
-            ir_add_analysis_trace(callee->ir_executable.analysis, note,
-                    buf_sprintf("depends on the frame here"));
             return ErrorSemanticAnalyzeFail;
         }
 
@@ -5454,6 +5626,37 @@ static Error resolve_async_frame(CodeGen *g, ZigType *frame_type) {
     return ErrorNone;
 }
 
+static Error resolve_pointer_zero_bits(CodeGen *g, ZigType *ty) {
+    Error err;
+
+    if (ty->abi_size != SIZE_MAX)
+        return ErrorNone;
+
+    if (ty->data.pointer.resolve_loop_flag_zero_bits) {
+        ty->abi_size = g->builtin_types.entry_usize->abi_size;
+        ty->size_in_bits = g->builtin_types.entry_usize->size_in_bits;
+        ty->abi_align = g->builtin_types.entry_usize->abi_align;
+        return ErrorNone;
+    }
+    ty->data.pointer.resolve_loop_flag_zero_bits = true;
+
+    ZigType *elem_type = ty->data.pointer.child_type;
+
+    if ((err = type_resolve(g, elem_type, ResolveStatusZeroBitsKnown)))
+        return err;
+
+    if (type_has_bits(elem_type)) {
+        ty->abi_size = g->builtin_types.entry_usize->abi_size;
+        ty->size_in_bits = g->builtin_types.entry_usize->size_in_bits;
+        ty->abi_align = g->builtin_types.entry_usize->abi_align;
+    } else {
+        ty->abi_size = 0;
+        ty->size_in_bits = 0;
+        ty->abi_align = 0;
+    }
+    return ErrorNone;
+}
+
 Error type_resolve(CodeGen *g, ZigType *ty, ResolveStatus status) {
     if (type_is_invalid(ty))
         return ErrorSemanticAnalyzeFail;
@@ -5463,36 +5666,48 @@ Error type_resolve(CodeGen *g, ZigType *ty, ResolveStatus status) {
         case ResolveStatusInvalid:
             zig_unreachable();
         case ResolveStatusZeroBitsKnown:
-            if (ty->id == ZigTypeIdStruct) {
-                return resolve_struct_zero_bits(g, ty);
-            } else if (ty->id == ZigTypeIdEnum) {
-                return resolve_enum_zero_bits(g, ty);
-            } else if (ty->id == ZigTypeIdUnion) {
-                return resolve_union_zero_bits(g, ty);
+            switch (ty->id) {
+                case ZigTypeIdStruct:
+                    return resolve_struct_zero_bits(g, ty);
+                case ZigTypeIdEnum:
+                    return resolve_enum_zero_bits(g, ty);
+                case ZigTypeIdUnion:
+                    return resolve_union_zero_bits(g, ty);
+                case ZigTypeIdPointer:
+                    return resolve_pointer_zero_bits(g, ty);
+                default:
+                    return ErrorNone;
             }
-            return ErrorNone;
         case ResolveStatusAlignmentKnown:
-            if (ty->id == ZigTypeIdStruct) {
-                return resolve_struct_alignment(g, ty);
-            } else if (ty->id == ZigTypeIdEnum) {
-                return resolve_enum_zero_bits(g, ty);
-            } else if (ty->id == ZigTypeIdUnion) {
-                return resolve_union_alignment(g, ty);
-            } else if (ty->id == ZigTypeIdFnFrame) {
-                return resolve_async_frame(g, ty);
+            switch (ty->id) {
+                case ZigTypeIdStruct:
+                    return resolve_struct_alignment(g, ty);
+                case ZigTypeIdEnum:
+                    return resolve_enum_zero_bits(g, ty);
+                case ZigTypeIdUnion:
+                    return resolve_union_alignment(g, ty);
+                case ZigTypeIdFnFrame:
+                    return resolve_async_frame(g, ty);
+                case ZigTypeIdPointer:
+                    return resolve_pointer_zero_bits(g, ty);
+                default:
+                    return ErrorNone;
             }
-            return ErrorNone;
         case ResolveStatusSizeKnown:
-            if (ty->id == ZigTypeIdStruct) {
-                return resolve_struct_type(g, ty);
-            } else if (ty->id == ZigTypeIdEnum) {
-                return resolve_enum_zero_bits(g, ty);
-            } else if (ty->id == ZigTypeIdUnion) {
-                return resolve_union_type(g, ty);
-            } else if (ty->id == ZigTypeIdFnFrame) {
-                return resolve_async_frame(g, ty);
+            switch (ty->id) {
+                case ZigTypeIdStruct:
+                    return resolve_struct_type(g, ty);
+                case ZigTypeIdEnum:
+                    return resolve_enum_zero_bits(g, ty);
+                case ZigTypeIdUnion:
+                    return resolve_union_type(g, ty);
+                case ZigTypeIdFnFrame:
+                    return resolve_async_frame(g, ty);
+                case ZigTypeIdPointer:
+                    return resolve_pointer_zero_bits(g, ty);
+                default:
+                    return ErrorNone;
             }
-            return ErrorNone;
         case ResolveStatusLLVMFwdDecl:
         case ResolveStatusLLVMFull:
             resolve_llvm_types(g, ty, status);
@@ -5867,6 +6082,9 @@ void render_const_value(CodeGen *g, Buf *buf, ConstExprValue *const_val) {
         case ConstValSpecialRuntime:
             buf_appendf(buf, "(runtime value)");
             return;
+        case ConstValSpecialLazy:
+            buf_appendf(buf, "(lazy value)");
+            return;
         case ConstValSpecialUndef:
             buf_appendf(buf, "undefined");
             return;
@@ -6241,6 +6459,40 @@ bool zig_llvm_fn_key_eql(ZigLLVMFnKey a, ZigLLVMFnKey b) {
     zig_unreachable();
 }
 
+static void init_const_undefined(CodeGen *g, ConstExprValue *const_val) {
+    Error err;
+    ZigType *wanted_type = const_val->type;
+    if (wanted_type->id == ZigTypeIdArray) {
+        const_val->special = ConstValSpecialStatic;
+        const_val->data.x_array.special = ConstArraySpecialUndef;
+    } else if (wanted_type->id == ZigTypeIdStruct) {
+        if ((err = type_resolve(g, wanted_type, ResolveStatusZeroBitsKnown))) {
+            return;
+        }
+
+        const_val->special = ConstValSpecialStatic;
+        size_t field_count = wanted_type->data.structure.src_field_count;
+        const_val->data.x_struct.fields = create_const_vals(field_count);
+        for (size_t i = 0; i < field_count; i += 1) {
+            ConstExprValue *field_val = &const_val->data.x_struct.fields[i];
+            field_val->type = wanted_type->data.structure.fields[i].type_entry;
+            assert(field_val->type);
+            init_const_undefined(g, field_val);
+            field_val->parent.id = ConstParentIdStruct;
+            field_val->parent.data.p_struct.struct_val = const_val;
+            field_val->parent.data.p_struct.field_index = i;
+        }
+    } else {
+        const_val->special = ConstValSpecialUndef;
+    }
+}
+
+void expand_undef_struct(CodeGen *g, ConstExprValue *const_val) {
+    if (const_val->special == ConstValSpecialUndef) {
+        init_const_undefined(g, const_val);
+    }
+}
+
 // Canonicalize the array value as ConstArraySpecialNone
 void expand_undef_array(CodeGen *g, ConstExprValue *const_val) {
     size_t elem_count;
@@ -6504,7 +6756,7 @@ bool type_ptr_eql(const ZigType *a, const ZigType *b) {
 
 ConstExprValue *get_builtin_value(CodeGen *codegen, const char *name) {
     Tld *tld = get_container_scope(codegen->compile_var_import)->decl_table.get(buf_create_from_str(name));
-    resolve_top_level_decl(codegen, tld, nullptr);
+    resolve_top_level_decl(codegen, tld, nullptr, false);
     assert(tld->id == TldIdVar);
     TldVar *tld_var = (TldVar *)tld;
     ConstExprValue *var_value = tld_var->var->const_value;
@@ -6719,19 +6971,6 @@ bool ptr_allows_addr_zero(ZigType *ptr_type) {
     return false;
 }
 
-void emit_error_notes_for_ref_stack(CodeGen *g, ErrorMsg *msg) {
-    size_t i = g->tld_ref_source_node_stack.length;
-    for (;;) {
-        if (i == 0)
-            break;
-        i -= 1;
-        AstNode *source_node = g->tld_ref_source_node_stack.at(i);
-        if (source_node) {
-            msg = add_error_note(g, msg, source_node, buf_sprintf("referenced here"));
-        }
-    }
-}
-
 Buf *type_bare_name(ZigType *type_entry) {
     if (is_slice(type_entry)) {
         return &type_entry->name;
@@ -7134,10 +7373,9 @@ static void resolve_llvm_types_struct(CodeGen *g, ZigType *struct_type, ResolveS
     struct_type->data.structure.resolve_status = ResolveStatusLLVMFull;
 }
 
-static void resolve_llvm_types_enum(CodeGen *g, ZigType *enum_type) {
-    assert(!enum_type->data.enumeration.is_invalid);
-    assert(enum_type->data.enumeration.complete);
-    if (enum_type->llvm_di_type != nullptr) return;
+static void resolve_llvm_types_enum(CodeGen *g, ZigType *enum_type, ResolveStatus wanted_resolve_status) {
+    assert(enum_type->data.enumeration.resolve_status >= ResolveStatusSizeKnown);
+    if (enum_type->data.enumeration.resolve_status >= wanted_resolve_status) return;
 
     Scope *scope = &enum_type->data.enumeration.decls_scope->base;
     ZigType *import = get_scope_import(scope);
@@ -7158,6 +7396,7 @@ static void resolve_llvm_types_enum(CodeGen *g, ZigType *enum_type) {
                 debug_align_in_bits,
                 ZigLLVM_DIFlags_Zero,
                 nullptr, di_element_types, (int)debug_field_count, 0, nullptr, "");
+        enum_type->data.enumeration.resolve_status = ResolveStatusLLVMFull;
         return;
     }
 
@@ -7190,14 +7429,16 @@ static void resolve_llvm_types_enum(CodeGen *g, ZigType *enum_type) {
             get_llvm_di_type(g, tag_int_type), "");
 
     enum_type->llvm_di_type = tag_di_type;
+    enum_type->data.enumeration.resolve_status = ResolveStatusLLVMFull;
 }
 
 static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveStatus wanted_resolve_status) {
     if (union_type->data.unionation.resolve_status >= wanted_resolve_status) return;
 
-    ZigType *most_aligned_union_member = union_type->data.unionation.most_aligned_union_member;
+    TypeUnionField *most_aligned_union_member = union_type->data.unionation.most_aligned_union_member;
     ZigType *tag_type = union_type->data.unionation.tag_type;
-    if (most_aligned_union_member == nullptr) {
+    uint32_t gen_field_count = union_type->data.unionation.gen_field_count;
+    if (gen_field_count == 0) {
         union_type->llvm_type = get_llvm_type(g, tag_type);
         union_type->llvm_di_type = get_llvm_di_type(g, tag_type);
         union_type->data.unionation.resolve_status = ResolveStatusLLVMFull;
@@ -7221,7 +7462,6 @@ static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveSta
         if (ResolveStatusLLVMFwdDecl >= wanted_resolve_status) return;
     }
 
-    uint32_t gen_field_count = union_type->data.unionation.gen_field_count;
     ZigLLVMDIType **union_inner_di_types = allocate<ZigLLVMDIType*>(gen_field_count);
     uint32_t field_count = union_type->data.unionation.src_field_count;
     for (uint32_t i = 0; i < field_count; i += 1) {
@@ -7248,17 +7488,17 @@ static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveSta
     if (tag_type == nullptr || !type_has_bits(tag_type)) {
         assert(most_aligned_union_member != nullptr);
 
-        size_t padding_bytes = union_type->data.unionation.union_abi_size - most_aligned_union_member->abi_size;
+        size_t padding_bytes = union_type->data.unionation.union_abi_size - most_aligned_union_member->type_entry->abi_size;
         if (padding_bytes > 0) {
             ZigType *u8_type = get_int_type(g, false, 8);
             ZigType *padding_array = get_array_type(g, u8_type, padding_bytes);
             LLVMTypeRef union_element_types[] = {
-                most_aligned_union_member->llvm_type,
+                most_aligned_union_member->type_entry->llvm_type,
                 get_llvm_type(g, padding_array),
             };
             LLVMStructSetBody(union_type->llvm_type, union_element_types, 2, false);
         } else {
-            LLVMStructSetBody(union_type->llvm_type, &most_aligned_union_member->llvm_type, 1, false);
+            LLVMStructSetBody(union_type->llvm_type, &most_aligned_union_member->type_entry->llvm_type, 1, false);
         }
         union_type->data.unionation.union_llvm_type = union_type->llvm_type;
         union_type->data.unionation.gen_tag_index = SIZE_MAX;
@@ -7269,7 +7509,7 @@ static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveSta
             ZigLLVMFileToScope(import->data.structure.root_struct->di_file), buf_ptr(&union_type->name),
             import->data.structure.root_struct->di_file, (unsigned)(decl_node->line + 1),
             union_type->data.unionation.union_abi_size * 8,
-            most_aligned_union_member->abi_align * 8,
+            most_aligned_union_member->align * 8,
             ZigLLVM_DIFlags_Zero, union_inner_di_types,
             gen_field_count, 0, "");
 
@@ -7280,14 +7520,14 @@ static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveSta
     }
 
     LLVMTypeRef union_type_ref;
-    size_t padding_bytes = union_type->data.unionation.union_abi_size - most_aligned_union_member->abi_size;
+    size_t padding_bytes = union_type->data.unionation.union_abi_size - most_aligned_union_member->type_entry->abi_size;
     if (padding_bytes == 0) {
-        union_type_ref = get_llvm_type(g, most_aligned_union_member);
+        union_type_ref = get_llvm_type(g, most_aligned_union_member->type_entry);
     } else {
         ZigType *u8_type = get_int_type(g, false, 8);
         ZigType *padding_array = get_array_type(g, u8_type, padding_bytes);
         LLVMTypeRef union_element_types[] = {
-            get_llvm_type(g, most_aligned_union_member),
+            get_llvm_type(g, most_aligned_union_member->type_entry),
             get_llvm_type(g, padding_array),
         };
         union_type_ref = LLVMStructType(union_element_types, 2, false);
@@ -7303,7 +7543,7 @@ static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveSta
     ZigLLVMDIType *union_di_type = ZigLLVMCreateDebugUnionType(g->dbuilder,
             ZigLLVMTypeToScope(union_type->llvm_di_type), "AnonUnion",
             import->data.structure.root_struct->di_file, (unsigned)(decl_node->line + 1),
-            most_aligned_union_member->size_in_bits, 8*most_aligned_union_member->abi_align,
+            most_aligned_union_member->type_entry->size_in_bits, 8*most_aligned_union_member->align,
             ZigLLVM_DIFlags_Zero, union_inner_di_types, gen_field_count, 0, "");
 
     uint64_t union_offset_in_bits = 8*LLVMOffsetOfElement(g->target_data_ref, union_type->llvm_type,
@@ -7314,8 +7554,8 @@ static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveSta
     ZigLLVMDIType *union_member_di_type = ZigLLVMCreateDebugMemberType(g->dbuilder,
             ZigLLVMTypeToScope(union_type->llvm_di_type), "payload",
             import->data.structure.root_struct->di_file, (unsigned)(decl_node->line + 1),
-            most_aligned_union_member->size_in_bits,
-            8*most_aligned_union_member->abi_align,
+            most_aligned_union_member->type_entry->size_in_bits,
+            8*most_aligned_union_member->align,
             union_offset_in_bits,
             ZigLLVM_DIFlags_Zero, union_di_type);
 
@@ -7352,6 +7592,9 @@ static void resolve_llvm_types_union(CodeGen *g, ZigType *union_type, ResolveSta
 static void resolve_llvm_types_pointer(CodeGen *g, ZigType *type, ResolveStatus wanted_resolve_status) {
     if (type->llvm_di_type != nullptr) return;
 
+    if (resolve_pointer_zero_bits(g, type) != ErrorNone)
+        zig_unreachable();
+
     if (!type_has_bits(type)) {
         type->llvm_type = g->builtin_types.entry_void->llvm_type;
         type->llvm_di_type = g->builtin_types.entry_void->llvm_di_type;
@@ -7921,7 +8164,7 @@ static void resolve_llvm_types(CodeGen *g, ZigType *type, ResolveStatus wanted_r
             else
                 return resolve_llvm_types_struct(g, type, wanted_resolve_status, nullptr);
         case ZigTypeIdEnum:
-            return resolve_llvm_types_enum(g, type);
+            return resolve_llvm_types_enum(g, type, wanted_resolve_status);
         case ZigTypeIdUnion:
             return resolve_llvm_types_union(g, type, wanted_resolve_status);
         case ZigTypeIdPointer:
diff --git a/src/analyze.hpp b/src/analyze.hpp
index 5752c74751..ef079a94cd 100644
--- a/src/analyze.hpp
+++ b/src/analyze.hpp
@@ -11,10 +11,9 @@
 #include "all_types.hpp"
 
 void semantic_analyze(CodeGen *g);
-ErrorMsg *add_node_error(CodeGen *g, const AstNode *node, Buf *msg);
+ErrorMsg *add_node_error(CodeGen *g, AstNode *node, Buf *msg);
 ErrorMsg *add_token_error(CodeGen *g, ZigType *owner, Token *token, Buf *msg);
 ErrorMsg *add_error_note(CodeGen *g, ErrorMsg *parent_msg, const AstNode *node, Buf *msg);
-void emit_error_notes_for_ref_stack(CodeGen *g, ErrorMsg *msg);
 ZigType *new_type_table_entry(ZigTypeId id);
 ZigType *get_fn_frame_type(CodeGen *g, ZigFn *fn);
 ZigType *get_pointer_to_type(CodeGen *g, ZigType *child_type, bool is_const);
@@ -59,7 +58,7 @@ ZigType *add_source_file(CodeGen *g, ZigPackage *package, Buf *abs_full_path, Bu
 ZigVar *find_variable(CodeGen *g, Scope *orig_context, Buf *name, ScopeFnDef **crossed_fndef_scope);
 Tld *find_decl(CodeGen *g, Scope *scope, Buf *name);
 Tld *find_container_decl(CodeGen *g, ScopeDecls *decls_scope, Buf *name);
-void resolve_top_level_decl(CodeGen *g, Tld *tld, AstNode *source_node);
+void resolve_top_level_decl(CodeGen *g, Tld *tld, AstNode *source_node, bool allow_lazy);
 
 ZigType *get_src_ptr_type(ZigType *type);
 ZigType *get_codegen_ptr_type(ZigType *type);
@@ -71,7 +70,6 @@ bool type_is_complete(ZigType *type_entry);
 bool type_is_resolved(ZigType *type_entry, ResolveStatus status);
 bool type_is_invalid(ZigType *type_entry);
 bool type_is_global_error_set(ZigType *err_set_type);
-Error resolve_container_type(CodeGen *g, ZigType *type_entry);
 ScopeDecls *get_container_scope(ZigType *type_entry);
 TypeStructField *find_struct_type_field(ZigType *type_entry, Buf *name);
 TypeEnumField *find_enum_type_field(ZigType *enum_type, Buf *name);
@@ -95,7 +93,6 @@ ZigFn *create_fn(CodeGen *g, AstNode *proto_node);
 ZigFn *create_fn_raw(CodeGen *g, FnInline inline_value);
 void init_fn_type_id(FnTypeId *fn_type_id, AstNode *proto_node, size_t param_count_alloc);
 AstNode *get_param_decl_node(ZigFn *fn_entry, size_t index);
-Error ATTRIBUTE_MUST_USE ensure_complete_type(CodeGen *g, ZigType *type_entry);
 Error ATTRIBUTE_MUST_USE type_resolve(CodeGen *g, ZigType *type_entry, ResolveStatus status);
 void complete_enum(CodeGen *g, ZigType *enum_type);
 bool ir_get_var_is_comptime(ZigVar *var);
@@ -169,12 +166,11 @@ ConstExprValue *create_const_slice(CodeGen *g, ConstExprValue *array_val, size_t
 void init_const_arg_tuple(CodeGen *g, ConstExprValue *const_val, size_t arg_index_start, size_t arg_index_end);
 ConstExprValue *create_const_arg_tuple(CodeGen *g, size_t arg_index_start, size_t arg_index_end);
 
-void init_const_undefined(CodeGen *g, ConstExprValue *const_val);
-
 ConstExprValue *create_const_vals(size_t count);
 
 ZigType *make_int_type(CodeGen *g, bool is_signed, uint32_t size_in_bits);
 void expand_undef_array(CodeGen *g, ConstExprValue *const_val);
+void expand_undef_struct(CodeGen *g, ConstExprValue *const_val);
 void update_compile_var(CodeGen *g, Buf *name, ConstExprValue *value);
 
 const char *type_id_name(ZigTypeId id);
@@ -244,9 +240,13 @@ void add_cc_args(CodeGen *g, ZigList<const char *> &args, const char *out_dep_pa
 
 void src_assert(bool ok, AstNode *source_node);
 bool is_container(ZigType *type_entry);
-ConstExprValue *analyze_const_value(CodeGen *g, Scope *scope, AstNode *node, ZigType *type_entry, Buf *type_name);
+ConstExprValue *analyze_const_value(CodeGen *g, Scope *scope, AstNode *node, ZigType *type_entry,
+        Buf *type_name, UndefAllowed undef);
 
 void resolve_llvm_types_fn(CodeGen *g, ZigFn *fn);
 bool fn_is_async(ZigFn *fn);
 
+Error type_val_resolve_abi_align(CodeGen *g, ConstExprValue *type_val, uint32_t *abi_align);
+ZigType *resolve_union_field_type(CodeGen *g, TypeUnionField *union_field);
+
 #endif
diff --git a/src/codegen.cpp b/src/codegen.cpp
index 6c87d3e0c3..e8724f0d22 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -3386,6 +3386,8 @@ static bool value_is_all_undef_array(ConstExprValue *const_val, size_t len) {
 
 static bool value_is_all_undef(ConstExprValue *const_val) {
     switch (const_val->special) {
+        case ConstValSpecialLazy:
+            zig_unreachable();
         case ConstValSpecialRuntime:
             return false;
         case ConstValSpecialUndef:
@@ -3525,6 +3527,8 @@ static LLVMValueRef ir_render_store_ptr(CodeGen *g, IrExecutable *executable, Ir
 }
 
 static LLVMValueRef ir_render_var_ptr(CodeGen *g, IrExecutable *executable, IrInstructionVarPtr *instruction) {
+    if (instruction->base.value.special != ConstValSpecialRuntime)
+        return ir_llvm_value(g, &instruction->base);
     ZigVar *var = instruction->var;
     if (type_has_bits(var->var_type)) {
         assert(var->value_ref);
@@ -6041,6 +6045,7 @@ static LLVMValueRef gen_const_ptr_union_recursive(CodeGen *g, ConstExprValue *un
 
 static LLVMValueRef pack_const_int(CodeGen *g, LLVMTypeRef big_int_type_ref, ConstExprValue *const_val) {
     switch (const_val->special) {
+        case ConstValSpecialLazy:
         case ConstValSpecialRuntime:
             zig_unreachable();
         case ConstValSpecialUndef:
@@ -6300,6 +6305,8 @@ static LLVMValueRef gen_const_val(CodeGen *g, ConstExprValue *const_val, const c
     assert(type_has_bits(type_entry));
 
     switch (const_val->special) {
+        case ConstValSpecialLazy:
+            zig_unreachable();
         case ConstValSpecialRuntime:
             zig_unreachable();
         case ConstValSpecialUndef:
@@ -6563,7 +6570,7 @@ static LLVMValueRef gen_const_val(CodeGen *g, ConstExprValue *const_val, const c
                     uint64_t pad_bytes = type_entry->data.unionation.union_abi_size - field_type_bytes;
                     LLVMValueRef correctly_typed_value = gen_const_val(g, payload_value, "");
                     make_unnamed_struct = is_llvm_value_unnamed_type(g, payload_value->type, correctly_typed_value) ||
-                        payload_value->type != type_entry->data.unionation.most_aligned_union_member;
+                        payload_value->type != type_entry->data.unionation.most_aligned_union_member->type_entry;
 
                     {
                         if (pad_bytes == 0) {
@@ -8891,7 +8898,7 @@ static void gen_root_source(CodeGen *g) {
         }
         Tld *panic_tld = find_decl(g, &get_container_scope(import_with_panic)->base, buf_create_from_str("panic"));
         assert(panic_tld != nullptr);
-        resolve_top_level_decl(g, panic_tld, nullptr);
+        resolve_top_level_decl(g, panic_tld, nullptr, false);
     }
 
 
diff --git a/src/ir.cpp b/src/ir.cpp
index 5251e6fb78..c1656a1711 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -152,11 +152,6 @@ struct ConstCastBadAllowsZero {
 };
 
 
-enum UndefAllowed {
-    UndefOk,
-    UndefBad,
-};
-
 static IrInstruction *ir_gen_node(IrBuilder *irb, AstNode *node, Scope *scope);
 static IrInstruction *ir_gen_node_extra(IrBuilder *irb, AstNode *node, Scope *scope, LVal lval,
         ResultLoc *result_loc);
@@ -234,6 +229,7 @@ static ConstExprValue *const_ptr_pointee_unchecked(CodeGen *g, ConstExprValue *c
         }
         case ConstPtrSpecialBaseStruct: {
             ConstExprValue *struct_val = const_val->data.x_ptr.data.base_struct.struct_val;
+            expand_undef_struct(g, struct_val);
             result = &struct_val->data.x_struct.fields[const_val->data.x_ptr.data.base_struct.field_index];
             break;
         }
@@ -402,7 +398,7 @@ static void ir_ref_var(ZigVar *var) {
 ZigType *ir_analyze_type_expr(IrAnalyze *ira, Scope *scope, AstNode *node) {
     ConstExprValue *result = ir_eval_const_value(ira->codegen, scope, node, ira->codegen->builtin_types.entry_type,
             ira->new_irb.exec->backward_branch_count, ira->new_irb.exec->backward_branch_quota, nullptr, nullptr,
-            node, nullptr, ira->new_irb.exec, nullptr);
+            node, nullptr, ira->new_irb.exec, nullptr, UndefBad);
 
     if (type_is_invalid(result->type))
         return ira->codegen->builtin_types.entry_invalid;
@@ -6858,7 +6854,7 @@ static IrInstruction *ir_gen_asm_expr(IrBuilder *irb, Scope *scope, AstNode *nod
                 uint32_t len = asm_token.end - asm_token.start - 2;
 
                 add_node_error(irb->codegen, node,
-                    buf_sprintf("could not find '%.*s' in the inputs or outputs.",
+                    buf_sprintf("could not find '%.*s' in the inputs or outputs",
                         len, ptr));
                 return irb->codegen->invalid_instruction;
             }
@@ -8111,7 +8107,12 @@ static IrInstruction *ir_gen_node_extra(IrBuilder *irb, AstNode *node, Scope *sc
         ir_build_reset_result(irb, scope, node, result_loc);
     }
     IrInstruction *result = ir_gen_node_raw(irb, node, scope, lval, result_loc);
-    irb->exec->invalid = irb->exec->invalid || (result == irb->codegen->invalid_instruction);
+    if (result == irb->codegen->invalid_instruction) {
+        if (irb->exec->first_err_trace_msg == nullptr) {
+            irb->exec->first_err_trace_msg = irb->codegen->trace_err;
+        }
+        src_assert(irb->exec->first_err_trace_msg != nullptr, node);
+    }
     return result;
 }
 
@@ -8119,21 +8120,20 @@ static IrInstruction *ir_gen_node(IrBuilder *irb, AstNode *node, Scope *scope) {
     return ir_gen_node_extra(irb, node, scope, LValNone, nullptr);
 }
 
-static void invalidate_exec(IrExecutable *exec) {
-    if (exec->invalid)
+static void invalidate_exec(IrExecutable *exec, ErrorMsg *msg) {
+    if (exec->first_err_trace_msg != nullptr)
         return;
 
-    exec->invalid = true;
+    exec->first_err_trace_msg = msg;
 
     for (size_t i = 0; i < exec->tld_list.length; i += 1) {
         exec->tld_list.items[i]->resolution = TldResolutionInvalid;
     }
 
     if (exec->source_exec != nullptr)
-        invalidate_exec(exec->source_exec);
+        invalidate_exec(exec->source_exec, msg);
 }
 
-
 bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_executable) {
     assert(node->owner);
 
@@ -8151,8 +8151,10 @@ bool ir_gen(CodeGen *codegen, AstNode *node, Scope *scope, IrExecutable *ir_exec
 
     IrInstruction *result = ir_gen_node_extra(irb, node, scope, LValNone, nullptr);
     assert(result);
-    if (irb->exec->invalid)
+    if (irb->exec->first_err_trace_msg != nullptr) {
+        codegen->trace_err = irb->exec->first_err_trace_msg;
         return false;
+    }
 
     if (!instr_is_unreachable(result)) {
         ir_mark_gen(ir_build_add_implicit_return_type(irb, scope, result->source_node, result));
@@ -8181,15 +8183,9 @@ static void ir_add_call_stack_errors(CodeGen *codegen, IrExecutable *exec, Error
     ir_add_call_stack_errors(codegen, exec->parent_exec, err_msg, limit - 1);
 }
 
-void ir_add_analysis_trace(IrAnalyze *ira, ErrorMsg *err_msg, Buf *text) {
-    IrInstruction *old_instruction = ira->old_irb.current_basic_block->instruction_list.at(ira->instruction_index);
-    add_error_note(ira->codegen, err_msg, old_instruction->source_node, text);
-    ir_add_call_stack_errors(ira->codegen, ira->new_irb.exec, err_msg, 10);
-}
-
 static ErrorMsg *exec_add_error_node(CodeGen *codegen, IrExecutable *exec, AstNode *source_node, Buf *msg) {
-    invalidate_exec(exec);
     ErrorMsg *err_msg = add_node_error(codegen, source_node, msg);
+    invalidate_exec(exec, err_msg);
     if (exec->parent_exec) {
         ir_add_call_stack_errors(codegen, exec, err_msg, 10);
     }
@@ -8223,6 +8219,7 @@ static Error eval_comptime_ptr_reinterpret(IrAnalyze *ira, CodeGen *codegen, Ast
 {
     Error err;
     assert(ptr_val->type->id == ZigTypeIdPointer);
+    assert(ptr_val->special == ConstValSpecialStatic);
     ConstExprValue tmp = {};
     tmp.special = ConstValSpecialStatic;
     tmp.type = ptr_val->type->data.pointer.child_type;
@@ -9016,7 +9013,8 @@ static bool ir_num_lit_fits_in_other_type(IrAnalyze *ira, IrInstruction *instruc
     }
 
     ConstExprValue *const_val = ir_resolve_const(ira, instruction, UndefBad);
-    assert(const_val != nullptr);
+    if (const_val == nullptr)
+        return false;
 
     bool const_val_is_int = (const_val->type->id == ZigTypeIdInt || const_val->type->id == ZigTypeIdComptimeInt);
     bool const_val_is_float = (const_val->type->id == ZigTypeIdFloat || const_val->type->id == ZigTypeIdComptimeFloat);
@@ -9376,6 +9374,14 @@ static ConstCastOnly types_match_const_cast_only(IrAnalyze *ira, ZigType *wanted
             result.id = ConstCastResultIdInvalid;
             return result;
         }
+        if ((err = type_resolve(g, wanted_type, ResolveStatusZeroBitsKnown))) {
+            result.id = ConstCastResultIdInvalid;
+            return result;
+        }
+        if ((err = type_resolve(g, actual_type, ResolveStatusZeroBitsKnown))) {
+            result.id = ConstCastResultIdInvalid;
+            return result;
+        }
         bool ptr_lens_equal = actual_ptr_type->data.pointer.ptr_len == wanted_ptr_type->data.pointer.ptr_len;
         if ((ptr_lens_equal || wanted_is_c_ptr || actual_is_c_ptr) &&
             type_has_bits(wanted_type) == type_has_bits(actual_type) &&
@@ -10634,7 +10640,7 @@ static void ir_finish_bb(IrAnalyze *ira) {
 
 static IrInstruction *ir_unreach_error(IrAnalyze *ira) {
     ira->old_bb_index = SIZE_MAX;
-    ira->new_irb.exec->invalid = true;
+    assert(ira->new_irb.exec->first_err_trace_msg != nullptr);
     return ira->codegen->unreach_instruction;
 }
 
@@ -10722,32 +10728,57 @@ static IrInstruction *ir_get_const_ptr(IrAnalyze *ira, IrInstruction *instructio
     return const_instr;
 }
 
+static Error ir_resolve_const_val(CodeGen *codegen, IrExecutable *exec, AstNode *source_node,
+        ConstExprValue *val, UndefAllowed undef_allowed)
+{
+    Error err;
+    for (;;) {
+        switch (val->special) {
+            case ConstValSpecialStatic:
+                return ErrorNone;
+            case ConstValSpecialRuntime:
+                if (!type_has_bits(val->type))
+                    return ErrorNone;
+
+                exec_add_error_node(codegen, exec, source_node,
+                        buf_sprintf("unable to evaluate constant expression"));
+                return ErrorSemanticAnalyzeFail;
+            case ConstValSpecialUndef:
+                if (undef_allowed == UndefOk || undef_allowed == LazyOk)
+                    return ErrorNone;
+
+                exec_add_error_node(codegen, exec, source_node,
+                        buf_sprintf("use of undefined value here causes undefined behavior"));
+                return ErrorSemanticAnalyzeFail;
+            case ConstValSpecialLazy:
+                if (undef_allowed == LazyOk || undef_allowed == LazyOkNoUndef)
+                    return ErrorNone;
+
+                if ((err = ir_resolve_lazy(codegen, source_node, val)))
+                    return err;
+
+                continue;
+        }
+    }
+}
+
 static ConstExprValue *ir_resolve_const(IrAnalyze *ira, IrInstruction *value, UndefAllowed undef_allowed) {
-    switch (value->value.special) {
-        case ConstValSpecialStatic:
-            return &value->value;
-        case ConstValSpecialRuntime:
-            if (!type_has_bits(value->value.type)) {
-                return &value->value;
-            }
-            ir_add_error(ira, value, buf_sprintf("unable to evaluate constant expression"));
-            return nullptr;
-        case ConstValSpecialUndef:
-            if (undef_allowed == UndefOk) {
-                return &value->value;
-            } else {
-                ir_add_error(ira, value, buf_sprintf("use of undefined value here causes undefined behavior"));
-                return nullptr;
-            }
+    Error err;
+    if ((err = ir_resolve_const_val(ira->codegen, ira->new_irb.exec, value->source_node,
+                    &value->value, undef_allowed)))
+    {
+        return nullptr;
     }
-    zig_unreachable();
+    return &value->value;
 }
 
 ConstExprValue *ir_eval_const_value(CodeGen *codegen, Scope *scope, AstNode *node,
         ZigType *expected_type, size_t *backward_branch_count, size_t *backward_branch_quota,
         ZigFn *fn_entry, Buf *c_import_buf, AstNode *source_node, Buf *exec_name,
-        IrExecutable *parent_exec, AstNode *expected_type_source_node)
+        IrExecutable *parent_exec, AstNode *expected_type_source_node, UndefAllowed undef_allowed)
 {
+    Error err;
+
     if (expected_type != nullptr && type_is_invalid(expected_type))
         return &codegen->invalid_instruction->value;
 
@@ -10761,8 +10792,10 @@ ConstExprValue *ir_eval_const_value(CodeGen *codegen, Scope *scope, AstNode *nod
     ir_executable->begin_scope = scope;
     ir_gen(codegen, node, scope, ir_executable);
 
-    if (ir_executable->invalid)
+    if (ir_executable->first_err_trace_msg != nullptr) {
+        codegen->trace_err = ir_executable->first_err_trace_msg;
         return &codegen->invalid_instruction->value;
+    }
 
     if (codegen->verbose_ir) {
         fprintf(stderr, "\nSource: ");
@@ -10783,8 +10816,9 @@ ConstExprValue *ir_eval_const_value(CodeGen *codegen, Scope *scope, AstNode *nod
     analyzed_executable->backward_branch_quota = backward_branch_quota;
     analyzed_executable->begin_scope = scope;
     ZigType *result_type = ir_analyze(codegen, ir_executable, analyzed_executable, expected_type, expected_type_source_node);
-    if (type_is_invalid(result_type))
+    if (type_is_invalid(result_type)) {
         return &codegen->invalid_instruction->value;
+    }
 
     if (codegen->verbose_ir) {
         fprintf(stderr, "{ // (analyzed)\n");
@@ -10792,7 +10826,14 @@ ConstExprValue *ir_eval_const_value(CodeGen *codegen, Scope *scope, AstNode *nod
         fprintf(stderr, "}\n");
     }
 
-    return ir_exec_const_result(codegen, analyzed_executable);
+    ConstExprValue *result = ir_exec_const_result(codegen, analyzed_executable);
+    if (type_is_invalid(result->type))
+        return &codegen->invalid_instruction->value;
+
+    if ((err = ir_resolve_const_val(codegen, analyzed_executable, node, result, undef_allowed)))
+        return &codegen->invalid_instruction->value;
+
+    return result;
 }
 
 static ErrorTableEntry *ir_resolve_error(IrAnalyze *ira, IrInstruction *err_value) {
@@ -10813,22 +10854,43 @@ static ErrorTableEntry *ir_resolve_error(IrAnalyze *ira, IrInstruction *err_valu
     return const_val->data.x_err_set;
 }
 
-static ZigType *ir_resolve_type(IrAnalyze *ira, IrInstruction *type_value) {
+static ZigType *ir_resolve_const_type(CodeGen *codegen, IrExecutable *exec, AstNode *source_node,
+        ConstExprValue *val)
+{
+    Error err;
+    if ((err = ir_resolve_const_val(codegen, exec, source_node, val, UndefBad)))
+        return codegen->builtin_types.entry_invalid;
+
+    assert(val->data.x_type != nullptr);
+    return val->data.x_type;
+}
+
+static ConstExprValue *ir_resolve_type_lazy(IrAnalyze *ira, IrInstruction *type_value) {
     if (type_is_invalid(type_value->value.type))
-        return ira->codegen->builtin_types.entry_invalid;
+        return nullptr;
 
     if (type_value->value.type->id != ZigTypeIdMetaType) {
         ir_add_error(ira, type_value,
                 buf_sprintf("expected type 'type', found '%s'", buf_ptr(&type_value->value.type->name)));
-        return ira->codegen->builtin_types.entry_invalid;
+        return nullptr;
     }
 
-    ConstExprValue *const_val = ir_resolve_const(ira, type_value, UndefBad);
-    if (!const_val)
+    Error err;
+    if ((err = ir_resolve_const_val(ira->codegen, ira->new_irb.exec, type_value->source_node,
+                    &type_value->value, LazyOk)))
+    {
+        return nullptr;
+    }
+
+    return &type_value->value;
+}
+
+static ZigType *ir_resolve_type(IrAnalyze *ira, IrInstruction *type_value) {
+    ConstExprValue *val = ir_resolve_type_lazy(ira, type_value);
+    if (val == nullptr)
         return ira->codegen->builtin_types.entry_invalid;
 
-    assert(const_val->data.x_type != nullptr);
-    return const_val->data.x_type;
+    return ir_resolve_const_type(ira->codegen, ira->new_irb.exec, type_value->source_node, val);
 }
 
 static ZigType *ir_resolve_int_type(IrAnalyze *ira, IrInstruction *type_value) {
@@ -11026,14 +11088,21 @@ static IrInstruction *ir_analyze_err_set_cast(IrAnalyze *ira, IrInstruction *sou
 }
 
 static IrInstruction *ir_analyze_frame_ptr_to_anyframe(IrAnalyze *ira, IrInstruction *source_instr,
-        IrInstruction *value, ZigType *wanted_type)
+        IrInstruction *frame_ptr, ZigType *wanted_type)
 {
-    if (instr_is_comptime(value)) {
-        zig_panic("TODO comptime frame pointer");
+    if (instr_is_comptime(frame_ptr)) {
+        ConstExprValue *ptr_val = ir_resolve_const(ira, frame_ptr, UndefBad);
+        if (ptr_val == nullptr)
+            return ira->codegen->invalid_instruction;
+
+        ir_assert(ptr_val->type->id == ZigTypeIdPointer, source_instr);
+        if (ptr_val->data.x_ptr.mut != ConstPtrMutRuntimeVar) {
+            zig_panic("TODO comptime frame pointer");
+        }
     }
 
     IrInstruction *result = ir_build_cast(&ira->new_irb, source_instr->scope, source_instr->source_node,
-            wanted_type, value, CastOpBitCast);
+            wanted_type, frame_ptr, CastOpBitCast);
     result->value.type = wanted_type;
     return result;
 }
@@ -11152,6 +11221,9 @@ static IrInstruction *ir_get_ref(IrAnalyze *ira, IrInstruction *source_instructi
     ZigType *ptr_type = get_pointer_to_type_extra(ira->codegen, value->value.type,
             is_const, is_volatile, PtrLenSingle, 0, 0, 0, false);
 
+    if ((err = type_resolve(ira->codegen, ptr_type, ResolveStatusZeroBitsKnown)))
+        return ira->codegen->invalid_instruction;
+
     IrInstruction *result_loc;
     if (type_has_bits(ptr_type) && !handle_is_ptr(value->value.type)) {
         result_loc = ir_resolve_result(ira, source_instruction, no_result_loc(), value->value.type, nullptr, true,
@@ -11322,7 +11394,7 @@ static IrInstruction *ir_analyze_undefined_to_anything(IrAnalyze *ira, IrInstruc
         IrInstruction *target, ZigType *wanted_type)
 {
     IrInstruction *result = ir_const(ira, source_instr, wanted_type);
-    init_const_undefined(ira->codegen, &result->value);
+    result->value.special = ConstValSpecialUndef;
     return result;
 }
 
@@ -11345,10 +11417,13 @@ static IrInstruction *ir_analyze_enum_to_union(IrAnalyze *ira, IrInstruction *so
             return ira->codegen->invalid_instruction;
         TypeUnionField *union_field = find_union_field_by_tag(wanted_type, &val->data.x_enum_tag);
         assert(union_field != nullptr);
-        if ((err = type_resolve(ira->codegen, union_field->type_entry, ResolveStatusZeroBitsKnown)))
+        ZigType *field_type = resolve_union_field_type(ira->codegen, union_field);
+        if (field_type == nullptr)
+            return ira->codegen->invalid_instruction;
+        if ((err = type_resolve(ira->codegen, field_type, ResolveStatusZeroBitsKnown)))
             return ira->codegen->invalid_instruction;
 
-        switch (type_has_one_possible_value(ira->codegen, union_field->type_entry)) {
+        switch (type_has_one_possible_value(ira->codegen, field_type)) {
             case OnePossibleValueInvalid:
                 return ira->codegen->invalid_instruction;
             case OnePossibleValueNo: {
@@ -11357,7 +11432,7 @@ static IrInstruction *ir_analyze_enum_to_union(IrAnalyze *ira, IrInstruction *so
                 ErrorMsg *msg = ir_add_error(ira, source_instr,
                         buf_sprintf("cast to union '%s' must initialize '%s' field '%s'",
                             buf_ptr(&wanted_type->name),
-                            buf_ptr(&union_field->type_entry->name),
+                            buf_ptr(&field_type->name),
                             buf_ptr(union_field->name)));
                 add_error_note(ira->codegen, msg, field_node,
                         buf_sprintf("field '%s' declared here", buf_ptr(union_field->name)));
@@ -11373,7 +11448,7 @@ static IrInstruction *ir_analyze_enum_to_union(IrAnalyze *ira, IrInstruction *so
         bigint_init_bigint(&result->value.data.x_union.tag, &val->data.x_enum_tag);
         result->value.data.x_union.payload = create_const_vals(1);
         result->value.data.x_union.payload->special = ConstValSpecialStatic;
-        result->value.data.x_union.payload->type = union_field->type_entry;
+        result->value.data.x_union.payload->type = field_type;
         return result;
     }
 
@@ -11390,12 +11465,17 @@ static IrInstruction *ir_analyze_enum_to_union(IrAnalyze *ira, IrInstruction *so
                 buf_ptr(&wanted_type->name)));
     for (uint32_t i = 0; i < wanted_type->data.unionation.src_field_count; i += 1) {
         TypeUnionField *union_field = &wanted_type->data.unionation.fields[i];
-        if (type_has_bits(union_field->type_entry)) {
+        ZigType *field_type = resolve_union_field_type(ira->codegen, union_field);
+        if (field_type == nullptr)
+            return ira->codegen->invalid_instruction;
+        if ((err = type_resolve(ira->codegen, field_type, ResolveStatusZeroBitsKnown)))
+            return ira->codegen->invalid_instruction;
+        if (type_has_bits(field_type)) {
             AstNode *field_node = wanted_type->data.unionation.decl_node->data.container_decl.fields.at(i);
             add_error_note(ira->codegen, msg, field_node,
                     buf_sprintf("field '%s' has type '%s'",
                         buf_ptr(union_field->name),
-                        buf_ptr(&union_field->type_entry->name)));
+                        buf_ptr(&field_type->name)));
         }
     }
     return ira->codegen->invalid_instruction;
@@ -11461,7 +11541,7 @@ static IrInstruction *ir_analyze_int_to_enum(IrAnalyze *ira, IrInstruction *sour
 
     ZigType *actual_type = target->value.type;
 
-    if ((err = ensure_complete_type(ira->codegen, wanted_type)))
+    if ((err = type_resolve(ira->codegen, wanted_type, ResolveStatusSizeKnown)))
         return ira->codegen->invalid_instruction;
 
     if (actual_type != wanted_type->data.enumeration.tag_int_type) {
@@ -12508,26 +12588,22 @@ static IrInstruction *ir_get_deref(IrAnalyze *ira, IrInstruction *source_instruc
     return ir_build_load_ptr_gen(ira, source_instruction, ptr, child_type, result_loc_inst);
 }
 
-static bool ir_resolve_align(IrAnalyze *ira, IrInstruction *value, uint32_t *out) {
-    if (type_is_invalid(value->value.type))
-        return false;
-
-    IrInstruction *casted_value = ir_implicit_cast(ira, value, get_align_amt_type(ira->codegen));
-    if (type_is_invalid(casted_value->value.type))
-        return false;
-
-    ConstExprValue *const_val = ir_resolve_const(ira, casted_value, UndefBad);
-    if (!const_val)
+static bool ir_resolve_const_align(CodeGen *codegen, IrExecutable *exec, AstNode *source_node,
+        ConstExprValue *const_val, uint32_t *out)
+{
+    Error err;
+    if ((err = ir_resolve_const_val(codegen, exec, source_node, const_val, UndefBad)))
         return false;
 
     uint32_t align_bytes = bigint_as_u32(&const_val->data.x_bigint);
     if (align_bytes == 0) {
-        ir_add_error(ira, value, buf_sprintf("alignment must be >= 1"));
+        exec_add_error_node(codegen, exec, source_node, buf_sprintf("alignment must be >= 1"));
         return false;
     }
 
     if (!is_power_of_2(align_bytes)) {
-        ir_add_error(ira, value, buf_sprintf("alignment value %" PRIu32 " is not a power of 2", align_bytes));
+        exec_add_error_node(codegen, exec, source_node,
+                buf_sprintf("alignment value %" PRIu32 " is not a power of 2", align_bytes));
         return false;
     }
 
@@ -12535,6 +12611,18 @@ static bool ir_resolve_align(IrAnalyze *ira, IrInstruction *value, uint32_t *out
     return true;
 }
 
+static bool ir_resolve_align(IrAnalyze *ira, IrInstruction *value, uint32_t *out) {
+    if (type_is_invalid(value->value.type))
+        return false;
+
+    IrInstruction *casted_value = ir_implicit_cast(ira, value, get_align_amt_type(ira->codegen));
+    if (type_is_invalid(casted_value->value.type))
+        return false;
+
+    return ir_resolve_const_align(ira->codegen, ira->new_irb.exec, value->source_node,
+            &casted_value->value, out);
+}
+
 static bool ir_resolve_unsigned(IrAnalyze *ira, IrInstruction *value, ZigType *int_type, uint64_t *out) {
     if (type_is_invalid(value->value.type))
         return false;
@@ -12719,7 +12807,9 @@ static IrInstruction *ir_analyze_instruction_return(IrAnalyze *ira, IrInstructio
     if (type_is_invalid(operand->value.type))
         return ir_unreach_error(ira);
 
-    if (!instr_is_comptime(operand) && handle_is_ptr(ira->explicit_return_type)) {
+    if (!instr_is_comptime(operand) && ira->explicit_return_type != nullptr &&
+            handle_is_ptr(ira->explicit_return_type))
+    {
         // result location mechanism took care of it.
         IrInstruction *result = ir_build_return(&ira->new_irb, instruction->base.scope,
                 instruction->base.source_node, nullptr);
@@ -13576,21 +13666,34 @@ static IrInstruction *ir_analyze_bin_op_math(IrAnalyze *ira, IrInstructionBinOp
         if (type_is_invalid(casted_op2->value.type))
             return ira->codegen->invalid_instruction;
 
-        if (op1->value.special == ConstValSpecialUndef || casted_op2->value.special == ConstValSpecialUndef) {
-            IrInstruction *result = ir_const(ira, &instruction->base, op1->value.type);
-            result->value.special = ConstValSpecialUndef;
-            return result;
+        // If either operand is undef, result is undef.
+        ConstExprValue *op1_val = nullptr;
+        ConstExprValue *op2_val = nullptr;
+        if (instr_is_comptime(op1)) {
+            op1_val = ir_resolve_const(ira, op1, UndefOk);
+            if (op1_val == nullptr)
+                return ira->codegen->invalid_instruction;
+            if (op1_val->special == ConstValSpecialUndef)
+                return ir_const_undef(ira, &instruction->base, op1->value.type);
+        }
+        if (instr_is_comptime(casted_op2)) {
+            op2_val = ir_resolve_const(ira, casted_op2, UndefOk);
+            if (op2_val == nullptr)
+                return ira->codegen->invalid_instruction;
+            if (op2_val->special == ConstValSpecialUndef)
+                return ir_const_undef(ira, &instruction->base, op1->value.type);
         }
-        if (casted_op2->value.special == ConstValSpecialStatic && op1->value.special == ConstValSpecialStatic &&
+
+        if (op2_val != nullptr && op1_val != nullptr &&
             (op1->value.data.x_ptr.special == ConstPtrSpecialHardCodedAddr ||
             op1->value.data.x_ptr.special == ConstPtrSpecialNull))
         {
-            uint64_t start_addr = (op1->value.data.x_ptr.special == ConstPtrSpecialNull) ?
-                0 : op1->value.data.x_ptr.data.hard_coded_addr.addr;
+            uint64_t start_addr = (op1_val->data.x_ptr.special == ConstPtrSpecialNull) ?
+                0 : op1_val->data.x_ptr.data.hard_coded_addr.addr;
             uint64_t elem_offset;
             if (!ir_resolve_usize(ira, casted_op2, &elem_offset))
                 return ira->codegen->invalid_instruction;
-            ZigType *elem_type = op1->value.type->data.pointer.child_type;
+            ZigType *elem_type = op1_val->type->data.pointer.child_type;
             if ((err = type_resolve(ira->codegen, elem_type, ResolveStatusSizeKnown)))
                 return ira->codegen->invalid_instruction;
             uint64_t byte_offset = type_size(ira->codegen, elem_type) * elem_offset;
@@ -13602,7 +13705,7 @@ static IrInstruction *ir_analyze_bin_op_math(IrAnalyze *ira, IrInstructionBinOp
             } else {
                 zig_unreachable();
             }
-            IrInstruction *result = ir_const(ira, &instruction->base, op1->value.type);
+            IrInstruction *result = ir_const(ira, &instruction->base, op1_val->type);
             result->value.data.x_ptr.special = ConstPtrSpecialHardCodedAddr;
             result->value.data.x_ptr.mut = ConstPtrMutRuntimeVar;
             result->value.data.x_ptr.data.hard_coded_addr.addr = new_addr;
@@ -14171,9 +14274,13 @@ static IrInstruction *ir_analyze_instruction_decl_var(IrAnalyze *ira,
         }
         break;
     case ReqCompTimeNo:
-        if (init_val != nullptr) {
-            if (init_val->special == ConstValSpecialStatic &&
-                init_val->type->id == ZigTypeIdFn &&
+        if (init_val != nullptr && value_is_comptime(init_val)) {
+            if ((err = ir_resolve_const_val(ira->codegen, ira->new_irb.exec,
+                    decl_var_instruction->base.source_node, init_val, UndefOk)))
+            {
+                result_type = ira->codegen->builtin_types.entry_invalid;
+            } else if (init_val->type->id == ZigTypeIdFn &&
+                init_val->special != ConstValSpecialUndef &&
                 init_val->data.x_ptr.special != ConstPtrSpecialHardCodedAddr &&
                 init_val->data.x_ptr.data.fn.fn_entry->fn_inline == FnInlineAlways)
             {
@@ -14231,7 +14338,7 @@ static IrInstruction *ir_analyze_instruction_decl_var(IrAnalyze *ira,
         }
     }
 
-    if (init_val != nullptr && init_val->special != ConstValSpecialRuntime) {
+    if (init_val != nullptr && value_is_comptime(init_val)) {
         // Resolve ConstPtrMutInfer
         if (var->gen_is_const) {
             var_ptr->value.data.x_ptr.mut = ConstPtrMutComptimeConst;
@@ -14242,6 +14349,10 @@ static IrInstruction *ir_analyze_instruction_decl_var(IrAnalyze *ira,
             // since it's a comptime val there are no instructions for it.
             // we memcpy the init value here
             IrInstruction *deref = ir_get_deref(ira, var_ptr, var_ptr, nullptr);
+            if (type_is_invalid(deref->value.type)) {
+                var->var_type = ira->codegen->builtin_types.entry_invalid;
+                return ira->codegen->invalid_instruction;
+            }
             // If this assertion trips, something is wrong with the IR instructions, because
             // we expected the above deref to return a constant value, but it created a runtime
             // instruction.
@@ -14250,7 +14361,7 @@ static IrInstruction *ir_analyze_instruction_decl_var(IrAnalyze *ira,
             ir_analyze_store_ptr(ira, var_ptr, var_ptr, deref, false);
         }
 
-        if (var_ptr->value.special == ConstValSpecialStatic && var->mem_slot_index != SIZE_MAX) {
+        if (instr_is_comptime(var_ptr) && var->mem_slot_index != SIZE_MAX) {
             assert(var->mem_slot_index < ira->exec_context.mem_slot_list.length);
             ConstExprValue *mem_slot = ira->exec_context.mem_slot_list.at(var->mem_slot_index);
             copy_const_val(mem_slot, init_val, !is_comptime_var || var->gen_is_const);
@@ -14555,6 +14666,10 @@ static IrInstruction *ir_analyze_alloca(IrAnalyze *ira, IrInstruction *source_in
 
     if ((err = type_resolve(ira->codegen, var_type, ResolveStatusZeroBitsKnown)))
         return ira->codegen->invalid_instruction;
+    if (align != 0) {
+        if ((err = type_resolve(ira->codegen, var_type, ResolveStatusAlignmentKnown)))
+            return ira->codegen->invalid_instruction;
+    }
     assert(result->base.value.data.x_ptr.special != ConstPtrSpecialInvalid);
 
     pointee->type = var_type;
@@ -15174,23 +15289,25 @@ static IrInstruction *ir_get_var_ptr(IrAnalyze *ira, IrInstruction *instruction,
 
     bool comptime_var_mem = ir_get_var_is_comptime(var);
     bool linkage_makes_it_runtime = var->decl_node->data.variable_declaration.is_extern;
-    bool is_const = var->src_is_const;
     bool is_volatile = false;
 
+    IrInstruction *result = ir_build_var_ptr(&ira->new_irb,
+            instruction->scope, instruction->source_node, var);
+    result->value.type = get_pointer_to_type_extra(ira->codegen, var->var_type,
+            var->src_is_const, is_volatile, PtrLenSingle, var->align_bytes, 0, 0, false);
+
     if (linkage_makes_it_runtime)
         goto no_mem_slot;
 
-    if (var->const_value->special == ConstValSpecialStatic) {
+    if (value_is_comptime(var->const_value)) {
         mem_slot = var->const_value;
-    } else {
-        if (var->mem_slot_index != SIZE_MAX && (comptime_var_mem || var->gen_is_const)) {
-            // find the relevant exec_context
-            assert(var->owner_exec != nullptr);
-            assert(var->owner_exec->analysis != nullptr);
-            IrExecContext *exec_context = &var->owner_exec->analysis->exec_context;
-            assert(var->mem_slot_index < exec_context->mem_slot_list.length);
-            mem_slot = exec_context->mem_slot_list.at(var->mem_slot_index);
-        }
+    } else if (var->mem_slot_index != SIZE_MAX && (comptime_var_mem || var->gen_is_const)) {
+        // find the relevant exec_context
+        assert(var->owner_exec != nullptr);
+        assert(var->owner_exec->analysis != nullptr);
+        IrExecContext *exec_context = &var->owner_exec->analysis->exec_context;
+        assert(var->mem_slot_index < exec_context->mem_slot_list.length);
+        mem_slot = exec_context->mem_slot_list.at(var->mem_slot_index);
     }
 
     if (mem_slot != nullptr) {
@@ -15198,6 +15315,7 @@ static IrInstruction *ir_get_var_ptr(IrAnalyze *ira, IrInstruction *instruction,
             case ConstValSpecialRuntime:
                 goto no_mem_slot;
             case ConstValSpecialStatic: // fallthrough
+            case ConstValSpecialLazy: // fallthrough
             case ConstValSpecialUndef: {
                 ConstPtrMut ptr_mut;
                 if (comptime_var_mem) {
@@ -15208,8 +15326,11 @@ static IrInstruction *ir_get_var_ptr(IrAnalyze *ira, IrInstruction *instruction,
                     assert(!comptime_var_mem);
                     ptr_mut = ConstPtrMutRuntimeVar;
                 }
-                return ir_get_const_ptr(ira, instruction, mem_slot, var->var_type,
-                        ptr_mut, is_const, is_volatile, var->align_bytes);
+                result->value.special = ConstValSpecialStatic;
+                result->value.data.x_ptr.mut = ptr_mut;
+                result->value.data.x_ptr.special = ConstPtrSpecialRef;
+                result->value.data.x_ptr.data.ref.pointee = mem_slot;
+                return result;
             }
         }
         zig_unreachable();
@@ -15217,15 +15338,10 @@ static IrInstruction *ir_get_var_ptr(IrAnalyze *ira, IrInstruction *instruction,
 
 no_mem_slot:
 
-    IrInstruction *var_ptr_instruction = ir_build_var_ptr(&ira->new_irb,
-            instruction->scope, instruction->source_node, var);
-    var_ptr_instruction->value.type = get_pointer_to_type_extra(ira->codegen, var->var_type,
-            var->src_is_const, is_volatile, PtrLenSingle, var->align_bytes, 0, 0, false);
-
     bool in_fn_scope = (scope_fn_entry(var->parent_scope) != nullptr);
-    var_ptr_instruction->value.data.rh_ptr = in_fn_scope ? RuntimeHintPtrStack : RuntimeHintPtrNonStack;
+    result->value.data.rh_ptr = in_fn_scope ? RuntimeHintPtrStack : RuntimeHintPtrNonStack;
 
-    return var_ptr_instruction;
+    return result;
 }
 
 // This function is called when a comptime value becomes accessible at runtime.
@@ -15489,7 +15605,8 @@ static IrInstruction *ir_analyze_fn_call(IrAnalyze *ira, IrInstructionCallSrc *c
             AstNode *body_node = fn_entry->body_node;
             result = ir_eval_const_value(ira->codegen, exec_scope, body_node, return_type,
                 ira->new_irb.exec->backward_branch_count, ira->new_irb.exec->backward_branch_quota, fn_entry,
-                nullptr, call_instruction->base.source_node, nullptr, ira->new_irb.exec, return_type_node);
+                nullptr, call_instruction->base.source_node, nullptr, ira->new_irb.exec, return_type_node,
+                UndefOk);
 
             if (inferred_err_set_type != nullptr) {
                 inferred_err_set_type->data.error_set.infer_fn = nullptr;
@@ -15513,8 +15630,9 @@ static IrInstruction *ir_analyze_fn_call(IrAnalyze *ira, IrInstructionCallSrc *c
                 ira->codegen->memoized_fn_eval_table.put(exec_scope, result);
             }
 
-            if (type_is_invalid(result->type))
+            if (type_is_invalid(result->type)) {
                 return ira->codegen->invalid_instruction;
+            }
         }
 
         IrInstruction *new_instruction = ir_const(ira, &call_instruction->base, result->type);
@@ -15685,7 +15803,8 @@ static IrInstruction *ir_analyze_fn_call(IrAnalyze *ira, IrInstructionCallSrc *c
             ConstExprValue *align_result = ir_eval_const_value(ira->codegen, impl_fn->child_scope,
                     fn_proto_node->data.fn_proto.align_expr, get_align_amt_type(ira->codegen),
                     ira->new_irb.exec->backward_branch_count, ira->new_irb.exec->backward_branch_quota,
-                    nullptr, nullptr, fn_proto_node->data.fn_proto.align_expr, nullptr, ira->new_irb.exec, nullptr);
+                    nullptr, nullptr, fn_proto_node->data.fn_proto.align_expr, nullptr, ira->new_irb.exec,
+                    nullptr, UndefBad);
             IrInstructionConst *const_instruction = ir_create_instruction<IrInstructionConst>(&ira->new_irb,
                     impl_fn->child_scope, fn_proto_node->data.fn_proto.align_expr);
             copy_const_val(&const_instruction->base.value, align_result, true);
@@ -16066,51 +16185,20 @@ static Error ir_read_const_ptr(IrAnalyze *ira, CodeGen *codegen, AstNode *source
     zig_unreachable();
 }
 
-static IrInstruction *ir_analyze_optional_type(IrAnalyze *ira, IrInstructionUnOp *un_op_instruction) {
-    Error err;
-    IrInstruction *value = un_op_instruction->value->child;
-    ZigType *type_entry = ir_resolve_type(ira, value);
-    if (type_is_invalid(type_entry))
-        return ira->codegen->invalid_instruction;
-    if ((err = type_resolve(ira->codegen, type_entry, ResolveStatusSizeKnown)))
-        return ira->codegen->invalid_instruction;
+static IrInstruction *ir_analyze_optional_type(IrAnalyze *ira, IrInstructionUnOp *instruction) {
+    IrInstruction *result = ir_const(ira, &instruction->base, ira->codegen->builtin_types.entry_type);
+    result->value.special = ConstValSpecialLazy;
 
-    switch (type_entry->id) {
-        case ZigTypeIdInvalid:
-            zig_unreachable();
-        case ZigTypeIdMetaType:
-        case ZigTypeIdVoid:
-        case ZigTypeIdBool:
-        case ZigTypeIdInt:
-        case ZigTypeIdVector:
-        case ZigTypeIdFloat:
-        case ZigTypeIdPointer:
-        case ZigTypeIdArray:
-        case ZigTypeIdStruct:
-        case ZigTypeIdComptimeFloat:
-        case ZigTypeIdComptimeInt:
-        case ZigTypeIdEnumLiteral:
-        case ZigTypeIdUndefined:
-        case ZigTypeIdNull:
-        case ZigTypeIdOptional:
-        case ZigTypeIdErrorUnion:
-        case ZigTypeIdErrorSet:
-        case ZigTypeIdEnum:
-        case ZigTypeIdUnion:
-        case ZigTypeIdFn:
-        case ZigTypeIdBoundFn:
-        case ZigTypeIdArgTuple:
-        case ZigTypeIdFnFrame:
-        case ZigTypeIdAnyFrame:
-            return ir_const_type(ira, &un_op_instruction->base, get_optional_type(ira->codegen, type_entry));
+    LazyValueOptType *lazy_opt_type = allocate<LazyValueOptType>(1);
+    lazy_opt_type->ira = ira;
+    result->value.data.x_lazy = &lazy_opt_type->base;
+    lazy_opt_type->base.id = LazyValueIdOptType;
 
-        case ZigTypeIdUnreachable:
-        case ZigTypeIdOpaque:
-            ir_add_error_node(ira, un_op_instruction->base.source_node,
-                    buf_sprintf("type '%s' not optional", buf_ptr(&type_entry->name)));
-            return ira->codegen->invalid_instruction;
-    }
-    zig_unreachable();
+    lazy_opt_type->payload_type = instruction->value->child;
+    if (ir_resolve_type_lazy(ira, lazy_opt_type->payload_type) == nullptr)
+        return ira->codegen->invalid_instruction;
+
+    return result;
 }
 
 static ErrorMsg *ir_eval_negation_scalar(IrAnalyze *ira, IrInstruction *source_instr, ZigType *scalar_type,
@@ -16727,7 +16815,7 @@ static IrInstruction *ir_analyze_instruction_elem_ptr(IrAnalyze *ira, IrInstruct
         return ira->codegen->invalid_instruction;
 
     bool safety_check_on = elem_ptr_instruction->safety_check_on;
-    if ((err = ensure_complete_type(ira->codegen, return_type->data.pointer.child_type)))
+    if ((err = type_resolve(ira->codegen, return_type->data.pointer.child_type, ResolveStatusSizeKnown)))
         return ira->codegen->invalid_instruction;
 
     uint64_t elem_size = type_size(ira->codegen, return_type->data.pointer.child_type);
@@ -17005,7 +17093,7 @@ static IrInstruction *ir_analyze_container_member_access_inner(IrAnalyze *ira,
         auto entry = container_scope->decl_table.maybe_get(field_name);
         Tld *tld = entry ? entry->value : nullptr;
         if (tld && tld->id == TldIdFn) {
-            resolve_top_level_decl(ira->codegen, tld, source_instr->source_node);
+            resolve_top_level_decl(ira->codegen, tld, source_instr->source_node, false);
             if (tld->resolution == TldResolutionInvalid)
                 return ira->codegen->invalid_instruction;
             TldFn *tld_fn = (TldFn *)tld;
@@ -17038,6 +17126,7 @@ static IrInstruction *ir_analyze_container_member_access_inner(IrAnalyze *ira,
 static IrInstruction *ir_analyze_struct_field_ptr(IrAnalyze *ira, IrInstruction *source_instr,
         TypeStructField *field, IrInstruction *struct_ptr, ZigType *struct_type, bool initializing)
 {
+    Error err;
     switch (type_has_one_possible_value(ira->codegen, field->type_entry)) {
         case OnePossibleValueInvalid:
             return ira->codegen->invalid_instruction;
@@ -17048,9 +17137,9 @@ static IrInstruction *ir_analyze_struct_field_ptr(IrAnalyze *ira, IrInstruction
         case OnePossibleValueNo:
             break;
     }
+    if ((err = type_resolve(ira->codegen, struct_type, ResolveStatusAlignmentKnown)))
+        return ira->codegen->invalid_instruction;
     assert(struct_ptr->value.type->id == ZigTypeIdPointer);
-    bool is_packed = (struct_type->data.structure.layout == ContainerLayoutPacked);
-    uint32_t align_bytes = is_packed ? 1 : get_abi_alignment(ira->codegen, field->type_entry);
     uint32_t ptr_bit_offset = struct_ptr->value.type->data.pointer.bit_offset_in_host;
     uint32_t ptr_host_int_bytes = struct_ptr->value.type->data.pointer.host_int_bytes;
     uint32_t host_int_bytes_for_result_type = (ptr_host_int_bytes == 0) ?
@@ -17058,7 +17147,7 @@ static IrInstruction *ir_analyze_struct_field_ptr(IrAnalyze *ira, IrInstruction
     bool is_const = struct_ptr->value.type->data.pointer.is_const;
     bool is_volatile = struct_ptr->value.type->data.pointer.is_volatile;
     ZigType *ptr_type = get_pointer_to_type_extra(ira->codegen, field->type_entry,
-            is_const, is_volatile, PtrLenSingle, align_bytes,
+            is_const, is_volatile, PtrLenSingle, field->align,
             (uint32_t)(ptr_bit_offset + field->bit_offset_in_host),
             (uint32_t)host_int_bytes_for_result_type, false);
     if (instr_is_comptime(struct_ptr)) {
@@ -17113,7 +17202,7 @@ static IrInstruction *ir_analyze_container_field_ptr(IrAnalyze *ira, Buf *field_
     Error err;
 
     ZigType *bare_type = container_ref_type(container_type);
-    if ((err = ensure_complete_type(ira->codegen, bare_type)))
+    if ((err = type_resolve(ira->codegen, bare_type, ResolveStatusSizeKnown)))
         return ira->codegen->invalid_instruction;
 
     assert(container_ptr->value.type->id == ZigTypeIdPointer);
@@ -17243,23 +17332,22 @@ static void add_link_lib_symbol(IrAnalyze *ira, Buf *lib_name, Buf *symbol_name,
 }
 
 static IrInstruction *ir_error_dependency_loop(IrAnalyze *ira, IrInstruction *source_instr) {
-    ErrorMsg *msg = ir_add_error(ira, source_instr, buf_sprintf("dependency loop detected"));
-    emit_error_notes_for_ref_stack(ira->codegen, msg);
+    ir_add_error(ira, source_instr, buf_sprintf("dependency loop detected"));
     return ira->codegen->invalid_instruction;
 }
 
 static IrInstruction *ir_analyze_decl_ref(IrAnalyze *ira, IrInstruction *source_instruction, Tld *tld) {
-    resolve_top_level_decl(ira->codegen, tld, source_instruction->source_node);
-    if (tld->resolution == TldResolutionInvalid)
+    resolve_top_level_decl(ira->codegen, tld, source_instruction->source_node, true);
+    if (tld->resolution == TldResolutionInvalid) {
         return ira->codegen->invalid_instruction;
+    }
 
     switch (tld->id) {
         case TldIdContainer:
         case TldIdCompTime:
         case TldIdUsingNamespace:
             zig_unreachable();
-        case TldIdVar:
-        {
+        case TldIdVar: {
             TldVar *tld_var = (TldVar *)tld;
             ZigVar *var = tld_var->var;
             if (var == nullptr) {
@@ -17271,8 +17359,7 @@ static IrInstruction *ir_analyze_decl_ref(IrAnalyze *ira, IrInstruction *source_
 
             return ir_get_var_ptr(ira, source_instruction, var);
         }
-        case TldIdFn:
-        {
+        case TldIdFn: {
             TldFn *tld_fn = (TldFn *)tld;
             ZigFn *fn_entry = tld_fn->fn_entry;
             assert(fn_entry->type_entry);
@@ -17396,7 +17483,7 @@ static IrInstruction *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstruc
             return ira->codegen->invalid_instruction;
         } else if (is_container(child_type)) {
             if (child_type->id == ZigTypeIdEnum) {
-                if ((err = ensure_complete_type(ira->codegen, child_type)))
+                if ((err = type_resolve(ira->codegen, child_type, ResolveStatusSizeKnown)))
                     return ira->codegen->invalid_instruction;
 
                 TypeEnumField *field = find_enum_type_field(child_type, field_name);
@@ -17425,7 +17512,7 @@ static IrInstruction *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstruc
                     (child_type->data.unionation.decl_node->data.container_decl.init_arg_expr != nullptr ||
                     child_type->data.unionation.decl_node->data.container_decl.auto_enum))
             {
-                if ((err = ensure_complete_type(ira->codegen, child_type)))
+                if ((err = type_resolve(ira->codegen, child_type, ResolveStatusSizeKnown)))
                     return ira->codegen->invalid_instruction;
                 TypeUnionField *field = find_union_type_field(child_type, field_name);
                 if (field) {
@@ -17844,22 +17931,29 @@ static IrInstruction *ir_analyze_instruction_any_frame_type(IrAnalyze *ira,
 static IrInstruction *ir_analyze_instruction_slice_type(IrAnalyze *ira,
         IrInstructionSliceType *slice_type_instruction)
 {
-    Error err;
-    uint32_t align_bytes = 0;
+    IrInstruction *result = ir_const(ira, &slice_type_instruction->base, ira->codegen->builtin_types.entry_type);
+    result->value.special = ConstValSpecialLazy;
+
+    LazyValueSliceType *lazy_slice_type = allocate<LazyValueSliceType>(1);
+    lazy_slice_type->ira = ira;
+    result->value.data.x_lazy = &lazy_slice_type->base;
+    lazy_slice_type->base.id = LazyValueIdSliceType;
+
     if (slice_type_instruction->align_value != nullptr) {
-        if (!ir_resolve_align(ira, slice_type_instruction->align_value->child, &align_bytes))
+        lazy_slice_type->align_inst = slice_type_instruction->align_value->child;
+        if (ir_resolve_const(ira, lazy_slice_type->align_inst, LazyOk) == nullptr)
             return ira->codegen->invalid_instruction;
     }
 
-    ZigType *child_type = ir_resolve_type(ira, slice_type_instruction->child_type->child);
-    if (type_is_invalid(child_type))
+    lazy_slice_type->elem_type = ir_resolve_type(ira, slice_type_instruction->child_type->child);
+    if (type_is_invalid(lazy_slice_type->elem_type))
         return ira->codegen->invalid_instruction;
 
-    bool is_const = slice_type_instruction->is_const;
-    bool is_volatile = slice_type_instruction->is_volatile;
-    bool is_allow_zero = slice_type_instruction->is_allow_zero;
+    lazy_slice_type->is_const = slice_type_instruction->is_const;
+    lazy_slice_type->is_volatile = slice_type_instruction->is_volatile;
+    lazy_slice_type->is_allowzero = slice_type_instruction->is_allow_zero;
 
-    switch (child_type->id) {
+    switch (lazy_slice_type->elem_type->id) {
         case ZigTypeIdInvalid: // handled above
             zig_unreachable();
         case ZigTypeIdUnreachable:
@@ -17868,7 +17962,7 @@ static IrInstruction *ir_analyze_instruction_slice_type(IrAnalyze *ira,
         case ZigTypeIdArgTuple:
         case ZigTypeIdOpaque:
             ir_add_error_node(ira, slice_type_instruction->base.source_node,
-                    buf_sprintf("slice of type '%s' not allowed", buf_ptr(&child_type->name)));
+                    buf_sprintf("slice of type '%s' not allowed", buf_ptr(&lazy_slice_type->elem_type->name)));
             return ira->codegen->invalid_instruction;
         case ZigTypeIdMetaType:
         case ZigTypeIdVoid:
@@ -17891,18 +17985,9 @@ static IrInstruction *ir_analyze_instruction_slice_type(IrAnalyze *ira,
         case ZigTypeIdVector:
         case ZigTypeIdFnFrame:
         case ZigTypeIdAnyFrame:
-            {
-                ResolveStatus needed_status = (align_bytes == 0) ?
-                    ResolveStatusZeroBitsKnown : ResolveStatusAlignmentKnown;
-                if ((err = type_resolve(ira->codegen, child_type, needed_status)))
-                    return ira->codegen->invalid_instruction;
-                ZigType *slice_ptr_type = get_pointer_to_type_extra(ira->codegen, child_type,
-                        is_const, is_volatile, PtrLenUnknown, align_bytes, 0, 0, is_allow_zero);
-                ZigType *result_type = get_slice_type(ira->codegen, slice_ptr_type);
-                return ir_const_type(ira, &slice_type_instruction->base, result_type);
-            }
+            break;
     }
-    zig_unreachable();
+    return result;
 }
 
 static IrInstruction *ir_analyze_instruction_global_asm(IrAnalyze *ira, IrInstructionGlobalAsm *instruction) {
@@ -18008,7 +18093,7 @@ static IrInstruction *ir_analyze_instruction_array_type(IrAnalyze *ira,
         case ZigTypeIdFnFrame:
         case ZigTypeIdAnyFrame:
             {
-                if ((err = ensure_complete_type(ira->codegen, child_type)))
+                if ((err = type_resolve(ira->codegen, child_type, ResolveStatusSizeKnown)))
                     return ira->codegen->invalid_instruction;
                 ZigType *result_type = get_array_type(ira->codegen, child_type, size);
                 return ir_const_type(ira, &array_type_instruction->base, result_type);
@@ -18024,7 +18109,7 @@ static IrInstruction *ir_analyze_instruction_size_of(IrAnalyze *ira,
     IrInstruction *type_value = size_of_instruction->type_value->child;
     ZigType *type_entry = ir_resolve_type(ira, type_value);
 
-    if ((err = ensure_complete_type(ira->codegen, type_entry)))
+    if ((err = type_resolve(ira->codegen, type_entry, ResolveStatusSizeKnown)))
         return ira->codegen->invalid_instruction;
 
     switch (type_entry->id) {
@@ -18529,7 +18614,7 @@ static IrInstruction *ir_analyze_instruction_switch_target(IrAnalyze *ira,
         if (pointee_val->special == ConstValSpecialRuntime)
             pointee_val = nullptr;
     }
-    if ((err = ensure_complete_type(ira->codegen, target_type)))
+    if ((err = type_resolve(ira->codegen, target_type, ResolveStatusSizeKnown)))
         return ira->codegen->invalid_instruction;
 
     switch (target_type->id) {
@@ -19070,7 +19155,7 @@ static IrInstruction *ir_analyze_container_init_fields(IrAnalyze *ira, IrInstruc
             Scope *analyze_scope = &get_container_scope(container_type)->base;
             // memoize it
             field->init_val = analyze_const_value(ira->codegen, analyze_scope, init_node,
-                    field->type_entry, nullptr);
+                    field->type_entry, nullptr, UndefOk);
         }
         if (type_is_invalid(field->init_val->type))
             return ira->codegen->invalid_instruction;
@@ -19276,8 +19361,7 @@ static IrInstruction *ir_analyze_instruction_compile_err(IrAnalyze *ira,
     if (!msg_buf)
         return ira->codegen->invalid_instruction;
 
-    ErrorMsg *msg = ir_add_error(ira, &instruction->base, msg_buf);
-    emit_error_notes_for_ref_stack(ira->codegen, msg);
+    ir_add_error(ira, &instruction->base, msg_buf);
 
     return ira->codegen->invalid_instruction;
 }
@@ -19319,7 +19403,10 @@ static IrInstruction *ir_analyze_instruction_err_name(IrAnalyze *ira, IrInstruct
     ZigType *u8_ptr_type = get_pointer_to_type_extra(ira->codegen, ira->codegen->builtin_types.entry_u8,
             true, false, PtrLenUnknown, 0, 0, 0, false);
     ZigType *str_type = get_slice_type(ira->codegen, u8_ptr_type);
-    if (casted_value->value.special == ConstValSpecialStatic) {
+    if (instr_is_comptime(casted_value)) {
+        ConstExprValue *val = ir_resolve_const(ira, casted_value, UndefBad);
+        if (val == nullptr)
+            return ira->codegen->invalid_instruction;
         ErrorTableEntry *err = casted_value->value.data.x_err_set;
         if (!err->cached_error_name_val) {
             ConstExprValue *array_val = create_const_str_lit(ira->codegen, &err->name);
@@ -19391,7 +19478,7 @@ static IrInstruction *ir_analyze_instruction_field_parent_ptr(IrAnalyze *ira,
         return ira->codegen->invalid_instruction;
     }
 
-    if ((err = ensure_complete_type(ira->codegen, container_type)))
+    if ((err = type_resolve(ira->codegen, container_type, ResolveStatusSizeKnown)))
         return ira->codegen->invalid_instruction;
 
     TypeStructField *field = find_struct_type_field(container_type, field_name);
@@ -19470,7 +19557,7 @@ static TypeStructField *validate_byte_offset(IrAnalyze *ira,
         return nullptr;
 
     Error err;
-    if ((err = ensure_complete_type(ira->codegen, container_type)))
+    if ((err = type_resolve(ira->codegen, container_type, ResolveStatusSizeKnown)))
         return nullptr;
 
     Buf *field_name = ir_resolve_str(ira, field_name_value);
@@ -19574,11 +19661,9 @@ static ZigType *ir_type_info_get_type(IrAnalyze *ira, const char *type_name, Zig
 
     ZigVar *var = tld->var;
 
-    if ((err = ensure_complete_type(ira->codegen, var->const_value->type)))
-        return ira->codegen->builtin_types.entry_invalid;
-
     assert(var->const_value->type->id == ZigTypeIdMetaType);
-    return var->const_value->data.x_type;
+
+    return ir_resolve_const_type(ira->codegen, ira->new_irb.exec, nullptr, var->const_value);
 }
 
 static Error ir_make_type_info_decls(IrAnalyze *ira, IrInstruction *source_instr, ConstExprValue *out_val,
@@ -19594,15 +19679,15 @@ static Error ir_make_type_info_decls(IrAnalyze *ira, IrInstruction *source_instr
     ensure_field_index(type_info_declaration_type, "data", 2);
 
     ZigType *type_info_declaration_data_type = ir_type_info_get_type(ira, "Data", type_info_declaration_type);
-    if ((err = ensure_complete_type(ira->codegen, type_info_declaration_data_type)))
+    if ((err = type_resolve(ira->codegen, type_info_declaration_data_type, ResolveStatusSizeKnown)))
         return err;
 
     ZigType *type_info_fn_decl_type = ir_type_info_get_type(ira, "FnDecl", type_info_declaration_data_type);
-    if ((err = ensure_complete_type(ira->codegen, type_info_fn_decl_type)))
+    if ((err = type_resolve(ira->codegen, type_info_fn_decl_type, ResolveStatusSizeKnown)))
         return err;
 
     ZigType *type_info_fn_decl_inline_type = ir_type_info_get_type(ira, "Inline", type_info_fn_decl_type);
-    if ((err = ensure_complete_type(ira->codegen, type_info_fn_decl_inline_type)))
+    if ((err = type_resolve(ira->codegen, type_info_fn_decl_inline_type, ResolveStatusSizeKnown)))
         return err;
 
     // Loop through our declarations once to figure out how many declarations we will generate info for.
@@ -19613,7 +19698,7 @@ static Error ir_make_type_info_decls(IrAnalyze *ira, IrInstruction *source_instr
     while ((curr_entry = decl_it.next()) != nullptr) {
         // If the declaration is unresolved, force it to be resolved again.
         if (curr_entry->value->resolution == TldResolutionUnresolved) {
-            resolve_top_level_decl(ira->codegen, curr_entry->value, curr_entry->value->source_node);
+            resolve_top_level_decl(ira->codegen, curr_entry->value, curr_entry->value->source_node, false);
             if (curr_entry->value->resolution != TldResolutionOk) {
                 return ErrorSemanticAnalyzeFail;
             }
@@ -19673,7 +19758,7 @@ static Error ir_make_type_info_decls(IrAnalyze *ira, IrInstruction *source_instr
             case TldIdVar:
                 {
                     ZigVar *var = ((TldVar *)curr_entry->value)->var;
-                    if ((err = ensure_complete_type(ira->codegen, var->const_value->type)))
+                    if ((err = type_resolve(ira->codegen, var->const_value->type, ResolveStatusSizeKnown)))
                         return ErrorSemanticAnalyzeFail;
 
                     if (var->const_value->type->id == ZigTypeIdMetaType) {
@@ -19799,7 +19884,7 @@ static Error ir_make_type_info_decls(IrAnalyze *ira, IrInstruction *source_instr
             case TldIdContainer:
                 {
                     ZigType *type_entry = ((TldContainer *)curr_entry->value)->type_entry;
-                    if ((err = ensure_complete_type(ira->codegen, type_entry)))
+                    if ((err = type_resolve(ira->codegen, type_entry, ResolveStatusSizeKnown)))
                         return ErrorSemanticAnalyzeFail;
 
                     // This is a type.
@@ -19855,7 +19940,7 @@ static ConstExprValue *create_ptr_like_type_info(IrAnalyze *ira, ZigType *ptr_ty
         return nullptr;
 
     ZigType *type_info_pointer_type = ir_type_info_get_type(ira, "Pointer", nullptr);
-    assertNoError(ensure_complete_type(ira->codegen, type_info_pointer_type));
+    assertNoError(type_resolve(ira->codegen, type_info_pointer_type, ResolveStatusSizeKnown));
 
     ConstExprValue *result = create_const_vals(1);
     result->special = ConstValSpecialStatic;
@@ -19867,7 +19952,7 @@ static ConstExprValue *create_ptr_like_type_info(IrAnalyze *ira, ZigType *ptr_ty
     // size: Size
     ensure_field_index(result->type, "size", 0);
     ZigType *type_info_pointer_size_type = ir_type_info_get_type(ira, "Size", type_info_pointer_type);
-    assertNoError(ensure_complete_type(ira->codegen, type_info_pointer_size_type));
+    assertNoError(type_resolve(ira->codegen, type_info_pointer_size_type, ResolveStatusSizeKnown));
     fields[0].special = ConstValSpecialStatic;
     fields[0].type = type_info_pointer_size_type;
     bigint_init_unsigned(&fields[0].data.x_enum_tag, size_enum_index);
@@ -20581,7 +20666,7 @@ static IrInstruction *ir_analyze_instruction_c_import(IrAnalyze *ira, IrInstruct
     ZigType *void_type = ira->codegen->builtin_types.entry_void;
     ConstExprValue *cimport_result = ir_eval_const_value(ira->codegen, &cimport_scope->base, block_node, void_type,
         ira->new_irb.exec->backward_branch_count, ira->new_irb.exec->backward_branch_quota, nullptr,
-        &cimport_scope->buf, block_node, nullptr, nullptr, nullptr);
+        &cimport_scope->buf, block_node, nullptr, nullptr, nullptr, UndefBad);
     if (type_is_invalid(cimport_result->type))
         return ira->codegen->invalid_instruction;
 
@@ -21482,64 +21567,75 @@ static IrInstruction *ir_analyze_instruction_memset(IrAnalyze *ira, IrInstructio
         return ira->codegen->invalid_instruction;
 
     // TODO test this at comptime with u8 and non-u8 types
-    if (casted_dest_ptr->value.special == ConstValSpecialStatic &&
-        casted_byte->value.special == ConstValSpecialStatic &&
-        casted_count->value.special == ConstValSpecialStatic &&
-        casted_dest_ptr->value.data.x_ptr.special != ConstPtrSpecialHardCodedAddr &&
-        casted_dest_ptr->value.data.x_ptr.mut != ConstPtrMutRuntimeVar)
+    if (instr_is_comptime(casted_dest_ptr) &&
+        instr_is_comptime(casted_byte) &&
+        instr_is_comptime(casted_count))
     {
-        ConstExprValue *dest_ptr_val = &casted_dest_ptr->value;
+        ConstExprValue *dest_ptr_val = ir_resolve_const(ira, casted_dest_ptr, UndefBad);
+        if (dest_ptr_val == nullptr)
+            return ira->codegen->invalid_instruction;
 
-        ConstExprValue *dest_elements;
-        size_t start;
-        size_t bound_end;
-        switch (dest_ptr_val->data.x_ptr.special) {
-            case ConstPtrSpecialInvalid:
-            case ConstPtrSpecialDiscard:
-                zig_unreachable();
-            case ConstPtrSpecialRef:
-                dest_elements = dest_ptr_val->data.x_ptr.data.ref.pointee;
-                start = 0;
-                bound_end = 1;
-                break;
-            case ConstPtrSpecialBaseArray:
-                {
-                    ConstExprValue *array_val = dest_ptr_val->data.x_ptr.data.base_array.array_val;
-                    expand_undef_array(ira->codegen, array_val);
-                    dest_elements = array_val->data.x_array.data.s_none.elements;
-                    start = dest_ptr_val->data.x_ptr.data.base_array.elem_index;
-                    bound_end = array_val->type->data.array.len;
-                    break;
-                }
-            case ConstPtrSpecialBaseStruct:
-                zig_panic("TODO memset on const inner struct");
-            case ConstPtrSpecialBaseErrorUnionCode:
-                zig_panic("TODO memset on const inner error union code");
-            case ConstPtrSpecialBaseErrorUnionPayload:
-                zig_panic("TODO memset on const inner error union payload");
-            case ConstPtrSpecialBaseOptionalPayload:
-                zig_panic("TODO memset on const inner optional payload");
-            case ConstPtrSpecialHardCodedAddr:
-                zig_unreachable();
-            case ConstPtrSpecialFunction:
-                zig_panic("TODO memset on ptr cast from function");
-            case ConstPtrSpecialNull:
-                zig_panic("TODO memset on null ptr");
-        }
+        ConstExprValue *byte_val = ir_resolve_const(ira, casted_byte, UndefOk);
+        if (byte_val == nullptr)
+            return ira->codegen->invalid_instruction;
 
-        size_t count = bigint_as_usize(&casted_count->value.data.x_bigint);
-        size_t end = start + count;
-        if (end > bound_end) {
-            ir_add_error(ira, count_value, buf_sprintf("out of bounds pointer access"));
+        ConstExprValue *count_val = ir_resolve_const(ira, casted_count, UndefBad);
+        if (count_val == nullptr)
             return ira->codegen->invalid_instruction;
-        }
 
-        ConstExprValue *byte_val = &casted_byte->value;
-        for (size_t i = start; i < end; i += 1) {
-            copy_const_val(&dest_elements[i], byte_val, true);
-        }
+        if (casted_dest_ptr->value.data.x_ptr.special != ConstPtrSpecialHardCodedAddr &&
+            casted_dest_ptr->value.data.x_ptr.mut != ConstPtrMutRuntimeVar)
+        {
+            ConstExprValue *dest_elements;
+            size_t start;
+            size_t bound_end;
+            switch (dest_ptr_val->data.x_ptr.special) {
+                case ConstPtrSpecialInvalid:
+                case ConstPtrSpecialDiscard:
+                    zig_unreachable();
+                case ConstPtrSpecialRef:
+                    dest_elements = dest_ptr_val->data.x_ptr.data.ref.pointee;
+                    start = 0;
+                    bound_end = 1;
+                    break;
+                case ConstPtrSpecialBaseArray:
+                    {
+                        ConstExprValue *array_val = dest_ptr_val->data.x_ptr.data.base_array.array_val;
+                        expand_undef_array(ira->codegen, array_val);
+                        dest_elements = array_val->data.x_array.data.s_none.elements;
+                        start = dest_ptr_val->data.x_ptr.data.base_array.elem_index;
+                        bound_end = array_val->type->data.array.len;
+                        break;
+                    }
+                case ConstPtrSpecialBaseStruct:
+                    zig_panic("TODO memset on const inner struct");
+                case ConstPtrSpecialBaseErrorUnionCode:
+                    zig_panic("TODO memset on const inner error union code");
+                case ConstPtrSpecialBaseErrorUnionPayload:
+                    zig_panic("TODO memset on const inner error union payload");
+                case ConstPtrSpecialBaseOptionalPayload:
+                    zig_panic("TODO memset on const inner optional payload");
+                case ConstPtrSpecialHardCodedAddr:
+                    zig_unreachable();
+                case ConstPtrSpecialFunction:
+                    zig_panic("TODO memset on ptr cast from function");
+                case ConstPtrSpecialNull:
+                    zig_panic("TODO memset on null ptr");
+            }
 
-        return ir_const_void(ira, &instruction->base);
+            size_t count = bigint_as_usize(&count_val->data.x_bigint);
+            size_t end = start + count;
+            if (end > bound_end) {
+                ir_add_error(ira, count_value, buf_sprintf("out of bounds pointer access"));
+                return ira->codegen->invalid_instruction;
+            }
+
+            for (size_t i = start; i < end; i += 1) {
+                copy_const_val(&dest_elements[i], byte_val, true);
+            }
+
+            return ir_const_void(ira, &instruction->base);
+        }
     }
 
     IrInstruction *result = ir_build_memset(&ira->new_irb, instruction->base.scope, instruction->base.source_node,
@@ -21607,107 +21703,118 @@ static IrInstruction *ir_analyze_instruction_memcpy(IrAnalyze *ira, IrInstructio
 
     // TODO test this at comptime with u8 and non-u8 types
     // TODO test with dest ptr being a global runtime variable
-    if (casted_dest_ptr->value.special == ConstValSpecialStatic &&
-        casted_src_ptr->value.special == ConstValSpecialStatic &&
-        casted_count->value.special == ConstValSpecialStatic &&
-        casted_dest_ptr->value.data.x_ptr.special != ConstPtrSpecialHardCodedAddr)
+    if (instr_is_comptime(casted_dest_ptr) &&
+        instr_is_comptime(casted_src_ptr) &&
+        instr_is_comptime(casted_count))
     {
-        size_t count = bigint_as_usize(&casted_count->value.data.x_bigint);
+        ConstExprValue *dest_ptr_val = ir_resolve_const(ira, casted_dest_ptr, UndefBad);
+        if (dest_ptr_val == nullptr)
+            return ira->codegen->invalid_instruction;
 
-        ConstExprValue *dest_ptr_val = &casted_dest_ptr->value;
-        ConstExprValue *dest_elements;
-        size_t dest_start;
-        size_t dest_end;
-        switch (dest_ptr_val->data.x_ptr.special) {
-            case ConstPtrSpecialInvalid:
-            case ConstPtrSpecialDiscard:
-                zig_unreachable();
-            case ConstPtrSpecialRef:
-                dest_elements = dest_ptr_val->data.x_ptr.data.ref.pointee;
-                dest_start = 0;
-                dest_end = 1;
-                break;
-            case ConstPtrSpecialBaseArray:
-                {
-                    ConstExprValue *array_val = dest_ptr_val->data.x_ptr.data.base_array.array_val;
-                    expand_undef_array(ira->codegen, array_val);
-                    dest_elements = array_val->data.x_array.data.s_none.elements;
-                    dest_start = dest_ptr_val->data.x_ptr.data.base_array.elem_index;
-                    dest_end = array_val->type->data.array.len;
-                    break;
-                }
-            case ConstPtrSpecialBaseStruct:
-                zig_panic("TODO memcpy on const inner struct");
-            case ConstPtrSpecialBaseErrorUnionCode:
-                zig_panic("TODO memcpy on const inner error union code");
-            case ConstPtrSpecialBaseErrorUnionPayload:
-                zig_panic("TODO memcpy on const inner error union payload");
-            case ConstPtrSpecialBaseOptionalPayload:
-                zig_panic("TODO memcpy on const inner optional payload");
-            case ConstPtrSpecialHardCodedAddr:
-                zig_unreachable();
-            case ConstPtrSpecialFunction:
-                zig_panic("TODO memcpy on ptr cast from function");
-            case ConstPtrSpecialNull:
-                zig_panic("TODO memcpy on null ptr");
-        }
+        ConstExprValue *src_ptr_val = ir_resolve_const(ira, casted_src_ptr, UndefBad);
+        if (src_ptr_val == nullptr)
+            return ira->codegen->invalid_instruction;
 
-        if (dest_start + count > dest_end) {
-            ir_add_error(ira, &instruction->base, buf_sprintf("out of bounds pointer access"));
+        ConstExprValue *count_val = ir_resolve_const(ira, casted_count, UndefBad);
+        if (count_val == nullptr)
             return ira->codegen->invalid_instruction;
-        }
 
-        ConstExprValue *src_ptr_val = &casted_src_ptr->value;
-        ConstExprValue *src_elements;
-        size_t src_start;
-        size_t src_end;
+        if (dest_ptr_val->data.x_ptr.special != ConstPtrSpecialHardCodedAddr) {
+            size_t count = bigint_as_usize(&count_val->data.x_bigint);
 
-        switch (src_ptr_val->data.x_ptr.special) {
-            case ConstPtrSpecialInvalid:
-            case ConstPtrSpecialDiscard:
-                zig_unreachable();
-            case ConstPtrSpecialRef:
-                src_elements = src_ptr_val->data.x_ptr.data.ref.pointee;
-                src_start = 0;
-                src_end = 1;
-                break;
-            case ConstPtrSpecialBaseArray:
-                {
-                    ConstExprValue *array_val = src_ptr_val->data.x_ptr.data.base_array.array_val;
-                    expand_undef_array(ira->codegen, array_val);
-                    src_elements = array_val->data.x_array.data.s_none.elements;
-                    src_start = src_ptr_val->data.x_ptr.data.base_array.elem_index;
-                    src_end = array_val->type->data.array.len;
+            ConstExprValue *dest_elements;
+            size_t dest_start;
+            size_t dest_end;
+            switch (dest_ptr_val->data.x_ptr.special) {
+                case ConstPtrSpecialInvalid:
+                case ConstPtrSpecialDiscard:
+                    zig_unreachable();
+                case ConstPtrSpecialRef:
+                    dest_elements = dest_ptr_val->data.x_ptr.data.ref.pointee;
+                    dest_start = 0;
+                    dest_end = 1;
                     break;
-                }
-            case ConstPtrSpecialBaseStruct:
-                zig_panic("TODO memcpy on const inner struct");
-            case ConstPtrSpecialBaseErrorUnionCode:
-                zig_panic("TODO memcpy on const inner error union code");
-            case ConstPtrSpecialBaseErrorUnionPayload:
-                zig_panic("TODO memcpy on const inner error union payload");
-            case ConstPtrSpecialBaseOptionalPayload:
-                zig_panic("TODO memcpy on const inner optional payload");
-            case ConstPtrSpecialHardCodedAddr:
-                zig_unreachable();
-            case ConstPtrSpecialFunction:
-                zig_panic("TODO memcpy on ptr cast from function");
-            case ConstPtrSpecialNull:
-                zig_panic("TODO memcpy on null ptr");
-        }
+                case ConstPtrSpecialBaseArray:
+                    {
+                        ConstExprValue *array_val = dest_ptr_val->data.x_ptr.data.base_array.array_val;
+                        expand_undef_array(ira->codegen, array_val);
+                        dest_elements = array_val->data.x_array.data.s_none.elements;
+                        dest_start = dest_ptr_val->data.x_ptr.data.base_array.elem_index;
+                        dest_end = array_val->type->data.array.len;
+                        break;
+                    }
+                case ConstPtrSpecialBaseStruct:
+                    zig_panic("TODO memcpy on const inner struct");
+                case ConstPtrSpecialBaseErrorUnionCode:
+                    zig_panic("TODO memcpy on const inner error union code");
+                case ConstPtrSpecialBaseErrorUnionPayload:
+                    zig_panic("TODO memcpy on const inner error union payload");
+                case ConstPtrSpecialBaseOptionalPayload:
+                    zig_panic("TODO memcpy on const inner optional payload");
+                case ConstPtrSpecialHardCodedAddr:
+                    zig_unreachable();
+                case ConstPtrSpecialFunction:
+                    zig_panic("TODO memcpy on ptr cast from function");
+                case ConstPtrSpecialNull:
+                    zig_panic("TODO memcpy on null ptr");
+            }
 
-        if (src_start + count > src_end) {
-            ir_add_error(ira, &instruction->base, buf_sprintf("out of bounds pointer access"));
-            return ira->codegen->invalid_instruction;
-        }
+            if (dest_start + count > dest_end) {
+                ir_add_error(ira, &instruction->base, buf_sprintf("out of bounds pointer access"));
+                return ira->codegen->invalid_instruction;
+            }
 
-        // TODO check for noalias violations - this should be generalized to work for any function
+            ConstExprValue *src_elements;
+            size_t src_start;
+            size_t src_end;
 
-        for (size_t i = 0; i < count; i += 1) {
-            copy_const_val(&dest_elements[dest_start + i], &src_elements[src_start + i], true);
-        }
+            switch (src_ptr_val->data.x_ptr.special) {
+                case ConstPtrSpecialInvalid:
+                case ConstPtrSpecialDiscard:
+                    zig_unreachable();
+                case ConstPtrSpecialRef:
+                    src_elements = src_ptr_val->data.x_ptr.data.ref.pointee;
+                    src_start = 0;
+                    src_end = 1;
+                    break;
+                case ConstPtrSpecialBaseArray:
+                    {
+                        ConstExprValue *array_val = src_ptr_val->data.x_ptr.data.base_array.array_val;
+                        expand_undef_array(ira->codegen, array_val);
+                        src_elements = array_val->data.x_array.data.s_none.elements;
+                        src_start = src_ptr_val->data.x_ptr.data.base_array.elem_index;
+                        src_end = array_val->type->data.array.len;
+                        break;
+                    }
+                case ConstPtrSpecialBaseStruct:
+                    zig_panic("TODO memcpy on const inner struct");
+                case ConstPtrSpecialBaseErrorUnionCode:
+                    zig_panic("TODO memcpy on const inner error union code");
+                case ConstPtrSpecialBaseErrorUnionPayload:
+                    zig_panic("TODO memcpy on const inner error union payload");
+                case ConstPtrSpecialBaseOptionalPayload:
+                    zig_panic("TODO memcpy on const inner optional payload");
+                case ConstPtrSpecialHardCodedAddr:
+                    zig_unreachable();
+                case ConstPtrSpecialFunction:
+                    zig_panic("TODO memcpy on ptr cast from function");
+                case ConstPtrSpecialNull:
+                    zig_panic("TODO memcpy on null ptr");
+            }
 
-        return ir_const_void(ira, &instruction->base);
+            if (src_start + count > src_end) {
+                ir_add_error(ira, &instruction->base, buf_sprintf("out of bounds pointer access"));
+                return ira->codegen->invalid_instruction;
+            }
+
+            // TODO check for noalias violations - this should be generalized to work for any function
+
+            for (size_t i = 0; i < count; i += 1) {
+                copy_const_val(&dest_elements[dest_start + i], &src_elements[src_start + i], true);
+            }
+
+            return ir_const_void(ira, &instruction->base);
+        }
     }
 
     IrInstruction *result = ir_build_memcpy(&ira->new_irb, instruction->base.scope, instruction->base.source_node,
@@ -21877,6 +21984,11 @@ static IrInstruction *ir_analyze_instruction_slice(IrAnalyze *ira, IrInstruction
             if (slice_ptr == nullptr)
                 return ira->codegen->invalid_instruction;
 
+            if (slice_ptr->special == ConstValSpecialUndef) {
+                ir_add_error(ira, &instruction->base, buf_sprintf("slice of undefined"));
+                return ira->codegen->invalid_instruction;
+            }
+
             parent_ptr = &slice_ptr->data.x_struct.fields[slice_ptr_index];
             if (parent_ptr->special == ConstValSpecialUndef) {
                 ir_add_error(ira, &instruction->base, buf_sprintf("slice of undefined"));
@@ -22021,7 +22133,7 @@ static IrInstruction *ir_analyze_instruction_member_count(IrAnalyze *ira, IrInst
         return ira->codegen->invalid_instruction;
     ZigType *container_type = ir_resolve_type(ira, container);
 
-    if ((err = ensure_complete_type(ira->codegen, container_type)))
+    if ((err = type_resolve(ira->codegen, container_type, ResolveStatusSizeKnown)))
         return ira->codegen->invalid_instruction;
 
     uint64_t result;
@@ -22057,7 +22169,7 @@ static IrInstruction *ir_analyze_instruction_member_type(IrAnalyze *ira, IrInstr
     if (type_is_invalid(container_type))
         return ira->codegen->invalid_instruction;
 
-    if ((err = ensure_complete_type(ira->codegen, container_type)))
+    if ((err = type_resolve(ira->codegen, container_type, ResolveStatusSizeKnown)))
         return ira->codegen->invalid_instruction;
 
 
@@ -22100,7 +22212,7 @@ static IrInstruction *ir_analyze_instruction_member_name(IrAnalyze *ira, IrInstr
     if (type_is_invalid(container_type))
         return ira->codegen->invalid_instruction;
 
-    if ((err = ensure_complete_type(ira->codegen, container_type)))
+    if ((err = type_resolve(ira->codegen, container_type, ResolveStatusSizeKnown)))
         return ira->codegen->invalid_instruction;
 
     uint64_t member_index;
@@ -22249,53 +22361,24 @@ static IrInstruction *ir_analyze_instruction_frame_size(IrAnalyze *ira, IrInstru
 }
 
 static IrInstruction *ir_analyze_instruction_align_of(IrAnalyze *ira, IrInstructionAlignOf *instruction) {
-    Error err;
-    IrInstruction *type_value = instruction->type_value->child;
-    if (type_is_invalid(type_value->value.type))
-        return ira->codegen->invalid_instruction;
-    ZigType *type_entry = ir_resolve_type(ira, type_value);
+    // Here we create a lazy value in order to avoid resolving the alignment of the type
+    // immediately. This avoids false positive dependency loops such as:
+    // const Node = struct {
+    //     field: []align(@alignOf(Node)) Node,
+    // };
+    IrInstruction *result = ir_const(ira, &instruction->base, ira->codegen->builtin_types.entry_num_lit_int);
+    result->value.special = ConstValSpecialLazy;
+
+    LazyValueAlignOf *lazy_align_of = allocate<LazyValueAlignOf>(1);
+    lazy_align_of->ira = ira;
+    result->value.data.x_lazy = &lazy_align_of->base;
+    lazy_align_of->base.id = LazyValueIdAlignOf;
 
-    if ((err = type_resolve(ira->codegen, type_entry, ResolveStatusAlignmentKnown)))
+    lazy_align_of->target_type = instruction->type_value->child;
+    if (ir_resolve_type_lazy(ira, lazy_align_of->target_type) == nullptr)
         return ira->codegen->invalid_instruction;
 
-    switch (type_entry->id) {
-        case ZigTypeIdInvalid:
-            zig_unreachable();
-        case ZigTypeIdMetaType:
-        case ZigTypeIdUnreachable:
-        case ZigTypeIdComptimeFloat:
-        case ZigTypeIdComptimeInt:
-        case ZigTypeIdEnumLiteral:
-        case ZigTypeIdUndefined:
-        case ZigTypeIdNull:
-        case ZigTypeIdBoundFn:
-        case ZigTypeIdArgTuple:
-        case ZigTypeIdVoid:
-        case ZigTypeIdOpaque:
-            ir_add_error(ira, instruction->type_value,
-                    buf_sprintf("no align available for type '%s'", buf_ptr(&type_entry->name)));
-            return ira->codegen->invalid_instruction;
-        case ZigTypeIdBool:
-        case ZigTypeIdInt:
-        case ZigTypeIdFloat:
-        case ZigTypeIdPointer:
-        case ZigTypeIdArray:
-        case ZigTypeIdStruct:
-        case ZigTypeIdOptional:
-        case ZigTypeIdErrorUnion:
-        case ZigTypeIdErrorSet:
-        case ZigTypeIdEnum:
-        case ZigTypeIdUnion:
-        case ZigTypeIdFn:
-        case ZigTypeIdVector:
-        case ZigTypeIdFnFrame:
-        case ZigTypeIdAnyFrame:
-            {
-                uint64_t align_in_bytes = get_abi_alignment(ira->codegen, type_entry);
-                return ir_const_unsigned(ira, &instruction->base, align_in_bytes);
-            }
-    }
-    zig_unreachable();
+    return result;
 }
 
 static IrInstruction *ir_analyze_instruction_overflow_op(IrAnalyze *ira, IrInstructionOverflowOp *instruction) {
@@ -22359,13 +22442,26 @@ static IrInstruction *ir_analyze_instruction_overflow_op(IrAnalyze *ira, IrInstr
     if (type_is_invalid(casted_result_ptr->value.type))
         return ira->codegen->invalid_instruction;
 
-    if (casted_op1->value.special == ConstValSpecialStatic &&
-        casted_op2->value.special == ConstValSpecialStatic &&
-        casted_result_ptr->value.special == ConstValSpecialStatic)
+    if (instr_is_comptime(casted_op1) &&
+        instr_is_comptime(casted_op2) &&
+        instr_is_comptime(casted_result_ptr))
     {
-        BigInt *op1_bigint = &casted_op1->value.data.x_bigint;
-        BigInt *op2_bigint = &casted_op2->value.data.x_bigint;
-        ConstExprValue *pointee_val = const_ptr_pointee(ira, ira->codegen, &casted_result_ptr->value, casted_result_ptr->source_node);
+        ConstExprValue *op1_val = ir_resolve_const(ira, casted_op1, UndefBad);
+        if (op1_val == nullptr)
+            return ira->codegen->invalid_instruction;
+
+        ConstExprValue *op2_val = ir_resolve_const(ira, casted_op2, UndefBad);
+        if (op2_val == nullptr)
+            return ira->codegen->invalid_instruction;
+
+        ConstExprValue *result_val = ir_resolve_const(ira, casted_result_ptr, UndefBad);
+        if (result_val == nullptr)
+            return ira->codegen->invalid_instruction;
+
+        BigInt *op1_bigint = &op1_val->data.x_bigint;
+        BigInt *op2_bigint = &op2_val->data.x_bigint;
+        ConstExprValue *pointee_val = const_ptr_pointee(ira, ira->codegen, result_val,
+                casted_result_ptr->source_node);
         if (pointee_val == nullptr)
             return ira->codegen->invalid_instruction;
         BigInt *dest_bigint = &pointee_val->data.x_bigint;
@@ -22754,84 +22850,64 @@ static IrInstruction *ir_analyze_instruction_fn_proto(IrAnalyze *ira, IrInstruct
     AstNode *proto_node = instruction->base.source_node;
     assert(proto_node->type == NodeTypeFnProto);
 
+    IrInstruction *result = ir_const(ira, &instruction->base, ira->codegen->builtin_types.entry_type);
+    result->value.special = ConstValSpecialLazy;
+
+    LazyValueFnType *lazy_fn_type = allocate<LazyValueFnType>(1);
+    lazy_fn_type->ira = ira;
+    result->value.data.x_lazy = &lazy_fn_type->base;
+    lazy_fn_type->base.id = LazyValueIdFnType;
+
     if (proto_node->data.fn_proto.auto_err_set) {
         ir_add_error(ira, &instruction->base,
             buf_sprintf("inferring error set of return type valid only for function definitions"));
         return ira->codegen->invalid_instruction;
     }
 
-    FnTypeId fn_type_id = {0};
-    init_fn_type_id(&fn_type_id, proto_node, proto_node->data.fn_proto.params.length);
+    size_t param_count = proto_node->data.fn_proto.params.length;
+    lazy_fn_type->proto_node = proto_node;
+    lazy_fn_type->param_types = allocate<IrInstruction *>(param_count);
 
-    for (; fn_type_id.next_param_index < fn_type_id.param_count; fn_type_id.next_param_index += 1) {
-        AstNode *param_node = proto_node->data.fn_proto.params.at(fn_type_id.next_param_index);
+    for (size_t param_index = 0; param_index < param_count; param_index += 1) {
+        AstNode *param_node = proto_node->data.fn_proto.params.at(param_index);
         assert(param_node->type == NodeTypeParamDecl);
 
         bool param_is_var_args = param_node->data.param_decl.is_var_args;
         if (param_is_var_args) {
-            if (fn_type_id.cc == CallingConventionC) {
-                fn_type_id.param_count = fn_type_id.next_param_index;
-                continue;
-            } else if (fn_type_id.cc == CallingConventionUnspecified) {
-                return ir_const_type(ira, &instruction->base, get_generic_fn_type(ira->codegen, &fn_type_id));
+            if (proto_node->data.fn_proto.cc == CallingConventionC) {
+                break;
+            } else if (proto_node->data.fn_proto.cc == CallingConventionUnspecified) {
+                lazy_fn_type->is_generic = true;
+                return result;
             } else {
                 zig_unreachable();
             }
         }
-        FnTypeParamInfo *param_info = &fn_type_id.param_info[fn_type_id.next_param_index];
-        param_info->is_noalias = param_node->data.param_decl.is_noalias;
 
-        if (instruction->param_types[fn_type_id.next_param_index] == nullptr) {
-            param_info->type = nullptr;
-            return ir_const_type(ira, &instruction->base, get_generic_fn_type(ira->codegen, &fn_type_id));
-        } else {
-            IrInstruction *param_type_value = instruction->param_types[fn_type_id.next_param_index]->child;
-            if (type_is_invalid(param_type_value->value.type))
-                return ira->codegen->invalid_instruction;
-            ZigType *param_type = ir_resolve_type(ira, param_type_value);
-            switch (type_requires_comptime(ira->codegen, param_type)) {
-            case ReqCompTimeYes:
-                if (!calling_convention_allows_zig_types(fn_type_id.cc)) {
-                    ir_add_error(ira, param_type_value,
-                        buf_sprintf("parameter of type '%s' not allowed in function with calling convention '%s'",
-                            buf_ptr(&param_type->name), calling_convention_name(fn_type_id.cc)));
-                    return ira->codegen->invalid_instruction;
-                }
-                param_info->type = param_type;
-                fn_type_id.next_param_index += 1;
-                return ir_const_type(ira, &instruction->base, get_generic_fn_type(ira->codegen, &fn_type_id));
-            case ReqCompTimeInvalid:
-                return ira->codegen->invalid_instruction;
-            case ReqCompTimeNo:
-                break;
-            }
-            if (!type_has_bits(param_type) && !calling_convention_allows_zig_types(fn_type_id.cc)) {
-                ir_add_error(ira, param_type_value,
-                    buf_sprintf("parameter of type '%s' has 0 bits; not allowed in function with calling convention '%s'",
-                        buf_ptr(&param_type->name), calling_convention_name(fn_type_id.cc)));
-                return ira->codegen->invalid_instruction;
-            }
-            param_info->type = param_type;
+        if (instruction->param_types[param_index] == nullptr) {
+            lazy_fn_type->is_generic = true;
+            return result;
         }
 
+        IrInstruction *param_type_value = instruction->param_types[param_index]->child;
+        if (type_is_invalid(param_type_value->value.type))
+            return ira->codegen->invalid_instruction;
+        if (ir_resolve_const(ira, param_type_value, LazyOk) == nullptr)
+            return ira->codegen->invalid_instruction;
+        lazy_fn_type->param_types[param_index] = param_type_value;
     }
 
     if (instruction->align_value != nullptr) {
-        if (!ir_resolve_align(ira, instruction->align_value->child, &fn_type_id.alignment))
+        lazy_fn_type->align_inst = instruction->align_value->child;
+        if (ir_resolve_const(ira, lazy_fn_type->align_inst, LazyOk) == nullptr)
             return ira->codegen->invalid_instruction;
     }
 
-    IrInstruction *return_type_value = instruction->return_type->child;
-    fn_type_id.return_type = ir_resolve_type(ira, return_type_value);
-    if (type_is_invalid(fn_type_id.return_type))
-        return ira->codegen->invalid_instruction;
-    if (fn_type_id.return_type->id == ZigTypeIdOpaque) {
-        ir_add_error(ira, instruction->return_type,
-            buf_sprintf("return type cannot be opaque"));
-        return ira->codegen->invalid_instruction;
-    }
+    lazy_fn_type->return_type = instruction->return_type->child;
+    if (ir_resolve_const(ira, lazy_fn_type->return_type, LazyOk) == nullptr)
+         return ira->codegen->invalid_instruction;
 
-    return ir_const_type(ira, &instruction->base, get_fn_type(ira->codegen, &fn_type_id));
+    return result;
 }
 
 static IrInstruction *ir_analyze_instruction_test_comptime(IrAnalyze *ira, IrInstructionTestComptime *instruction) {
@@ -23218,7 +23294,7 @@ static IrInstruction *ir_analyze_ptr_cast(IrAnalyze *ira, IrInstruction *source_
         if (!val)
             return ira->codegen->invalid_instruction;
 
-        if (val->special == ConstValSpecialStatic) {
+        if (value_is_comptime(val) && val->special != ConstValSpecialUndef) {
             bool is_addr_zero = val->data.x_ptr.special == ConstPtrSpecialNull ||
                 (val->data.x_ptr.special == ConstPtrSpecialHardCodedAddr &&
                     val->data.x_ptr.data.hard_coded_addr.addr == 0);
@@ -23258,6 +23334,12 @@ static IrInstruction *ir_analyze_ptr_cast(IrAnalyze *ira, IrInstruction *source_
 
     IrInstruction *casted_ptr = ir_build_ptr_cast_gen(ira, source_instr, dest_type, ptr, safety_check_on);
 
+    if ((err = type_resolve(ira->codegen, dest_type, ResolveStatusZeroBitsKnown)))
+        return ira->codegen->invalid_instruction;
+
+    if ((err = type_resolve(ira->codegen, src_type, ResolveStatusZeroBitsKnown)))
+        return ira->codegen->invalid_instruction;
+
     if (type_has_bits(dest_type) && !type_has_bits(src_type)) {
         ErrorMsg *msg = ir_add_error(ira, source_instr,
             buf_sprintf("'%s' and '%s' do not have the same in-memory representation",
@@ -23309,8 +23391,10 @@ static void buf_write_value_bytes_array(CodeGen *codegen, uint8_t *buf, ConstExp
 }
 
 static void buf_write_value_bytes(CodeGen *codegen, uint8_t *buf, ConstExprValue *val) {
-    if (val->special == ConstValSpecialUndef)
+    if (val->special == ConstValSpecialUndef) {
+        expand_undef_struct(codegen, val);
         val->special = ConstValSpecialStatic;
+    }
     assert(val->special == ConstValSpecialStatic);
     switch (val->type->id) {
         case ZigTypeIdInvalid:
@@ -23746,8 +23830,9 @@ static IrInstruction *ir_analyze_instruction_decl_ref(IrAnalyze *ira,
         IrInstructionDeclRef *instruction)
 {
     IrInstruction *ref_instruction = ir_analyze_decl_ref(ira, &instruction->base, instruction->tld);
-    if (type_is_invalid(ref_instruction->value.type))
+    if (type_is_invalid(ref_instruction->value.type)) {
         return ira->codegen->invalid_instruction;
+    }
 
     if (instruction->lval == LValPtr) {
         return ref_instruction;
@@ -23795,53 +23880,32 @@ static IrInstruction *ir_analyze_instruction_ptr_to_int(IrAnalyze *ira, IrInstru
 }
 
 static IrInstruction *ir_analyze_instruction_ptr_type(IrAnalyze *ira, IrInstructionPtrType *instruction) {
-    Error err;
-    ZigType *child_type = ir_resolve_type(ira, instruction->child_type->child);
-    if (type_is_invalid(child_type))
-        return ira->codegen->invalid_instruction;
+    IrInstruction *result = ir_const(ira, &instruction->base, ira->codegen->builtin_types.entry_type);
+    result->value.special = ConstValSpecialLazy;
 
-    if (child_type->id == ZigTypeIdUnreachable) {
-        ir_add_error(ira, &instruction->base, buf_sprintf("pointer to noreturn not allowed"));
-        return ira->codegen->invalid_instruction;
-    } else if (child_type->id == ZigTypeIdOpaque && instruction->ptr_len == PtrLenUnknown) {
-        ir_add_error(ira, &instruction->base, buf_sprintf("unknown-length pointer to opaque"));
+    LazyValuePtrType *lazy_ptr_type = allocate<LazyValuePtrType>(1);
+    lazy_ptr_type->ira = ira;
+    result->value.data.x_lazy = &lazy_ptr_type->base;
+    lazy_ptr_type->base.id = LazyValueIdPtrType;
+
+    lazy_ptr_type->elem_type = instruction->child_type->child;
+    if (ir_resolve_type_lazy(ira, lazy_ptr_type->elem_type) == nullptr)
         return ira->codegen->invalid_instruction;
-    } else if (instruction->ptr_len == PtrLenC) {
-        if (!type_allowed_in_extern(ira->codegen, child_type)) {
-            ir_add_error(ira, &instruction->base,
-                buf_sprintf("C pointers cannot point to non-C-ABI-compatible type '%s'", buf_ptr(&child_type->name)));
-            return ira->codegen->invalid_instruction;
-        } else if (child_type->id == ZigTypeIdOpaque) {
-            ir_add_error(ira, &instruction->base, buf_sprintf("C pointers cannot point opaque types"));
-            return ira->codegen->invalid_instruction;
-        } else if (instruction->is_allow_zero) {
-            ir_add_error(ira, &instruction->base, buf_sprintf("C pointers always allow address zero"));
-            return ira->codegen->invalid_instruction;
-        }
-    }
 
-    uint32_t align_bytes;
     if (instruction->align_value != nullptr) {
-        if (!ir_resolve_align(ira, instruction->align_value->child, &align_bytes))
+        lazy_ptr_type->align_inst = instruction->align_value->child;
+        if (ir_resolve_const(ira, lazy_ptr_type->align_inst, LazyOk) == nullptr)
             return ira->codegen->invalid_instruction;
-        if ((err = type_resolve(ira->codegen, child_type, ResolveStatusAlignmentKnown)))
-            return ira->codegen->invalid_instruction;
-        if (!type_has_bits(child_type)) {
-            align_bytes = 0;
-        }
-    } else {
-        if ((err = type_resolve(ira->codegen, child_type, ResolveStatusZeroBitsKnown)))
-            return ira->codegen->invalid_instruction;
-        align_bytes = 0;
     }
 
-    bool allow_zero = instruction->is_allow_zero || instruction->ptr_len == PtrLenC;
+    lazy_ptr_type->ptr_len = instruction->ptr_len;
+    lazy_ptr_type->is_const = instruction->is_const;
+    lazy_ptr_type->is_volatile = instruction->is_volatile;
+    lazy_ptr_type->is_allowzero = instruction->is_allow_zero;
+    lazy_ptr_type->bit_offset_in_host = instruction->bit_offset_start;
+    lazy_ptr_type->host_int_bytes = instruction->host_int_bytes;
 
-    ZigType *result_type = get_pointer_to_type_extra(ira->codegen, child_type,
-            instruction->is_const, instruction->is_volatile,
-            instruction->ptr_len, align_bytes,
-            instruction->bit_offset_start, instruction->host_int_bytes, allow_zero);
-    return ir_const_type(ira, &instruction->base, result_type);
+    return result;
 }
 
 static IrInstruction *ir_analyze_instruction_align_cast(IrAnalyze *ira, IrInstructionAlignCast *instruction) {
@@ -23954,7 +24018,7 @@ static IrInstruction *ir_analyze_instruction_tag_type(IrAnalyze *ira, IrInstruct
         return ira->codegen->invalid_instruction;
 
     if (enum_type->id == ZigTypeIdEnum) {
-        if ((err = ensure_complete_type(ira->codegen, enum_type)))
+        if ((err = type_resolve(ira->codegen, enum_type, ResolveStatusSizeKnown)))
             return ira->codegen->invalid_instruction;
 
         return ir_const_type(ira, &instruction->base, enum_type->data.enumeration.tag_int_type);
@@ -25100,7 +25164,7 @@ static IrInstruction *ir_analyze_instruction_base(IrAnalyze *ira, IrInstruction
 ZigType *ir_analyze(CodeGen *codegen, IrExecutable *old_exec, IrExecutable *new_exec,
         ZigType *expected_type, AstNode *expected_type_source_node)
 {
-    assert(!old_exec->invalid);
+    assert(old_exec->first_err_trace_msg == nullptr);
     assert(expected_type == nullptr || !type_is_invalid(expected_type));
 
     IrAnalyze *ira = allocate<IrAnalyze>(1);
@@ -25147,6 +25211,18 @@ ZigType *ir_analyze(CodeGen *codegen, IrExecutable *old_exec, IrExecutable *new_
             old_instruction->child = new_instruction;
 
             if (type_is_invalid(new_instruction->value.type)) {
+                if (new_exec->first_err_trace_msg != nullptr) {
+                    ira->codegen->trace_err = new_exec->first_err_trace_msg;
+                } else {
+                    new_exec->first_err_trace_msg = ira->codegen->trace_err;
+                }
+                if (new_exec->first_err_trace_msg != nullptr &&
+                    !old_instruction->source_node->already_traced_this_node)
+                {
+                    old_instruction->source_node->already_traced_this_node = true;
+                    new_exec->first_err_trace_msg = add_error_note(ira->codegen, new_exec->first_err_trace_msg,
+                            old_instruction->source_node, buf_create_from_str("referenced here"));
+                }
                 return ira->codegen->builtin_types.entry_invalid;
             }
 
@@ -25158,7 +25234,15 @@ ZigType *ir_analyze(CodeGen *codegen, IrExecutable *old_exec, IrExecutable *new_
         ira->instruction_index += 1;
     }
 
-    if (new_exec->invalid) {
+    if (new_exec->first_err_trace_msg != nullptr) {
+        codegen->trace_err = new_exec->first_err_trace_msg;
+        if (codegen->trace_err != nullptr && new_exec->source_node != nullptr &&
+            !new_exec->source_node->already_traced_this_node)
+        {
+            new_exec->source_node->already_traced_this_node = true;
+            codegen->trace_err = add_error_note(codegen, codegen->trace_err,
+                    new_exec->source_node, buf_create_from_str("referenced here"));
+        }
         return ira->codegen->builtin_types.entry_invalid;
     } else if (ira->src_implicit_return_type_list.length == 0) {
         return codegen->builtin_types.entry_unreachable;
@@ -25354,3 +25438,269 @@ bool ir_has_side_effects(IrInstruction *instruction) {
     }
     zig_unreachable();
 }
+
+static ZigType *ir_resolve_lazy_fn_type(IrAnalyze *ira, AstNode *source_node, LazyValueFnType *lazy_fn_type) {
+    Error err;
+    AstNode *proto_node = lazy_fn_type->proto_node;
+
+    FnTypeId fn_type_id = {0};
+    init_fn_type_id(&fn_type_id, proto_node, proto_node->data.fn_proto.params.length);
+
+    for (; fn_type_id.next_param_index < fn_type_id.param_count; fn_type_id.next_param_index += 1) {
+        AstNode *param_node = proto_node->data.fn_proto.params.at(fn_type_id.next_param_index);
+        assert(param_node->type == NodeTypeParamDecl);
+
+        bool param_is_var_args = param_node->data.param_decl.is_var_args;
+        if (param_is_var_args) {
+            if (fn_type_id.cc == CallingConventionC) {
+                fn_type_id.param_count = fn_type_id.next_param_index;
+                continue;
+            } else if (fn_type_id.cc == CallingConventionUnspecified) {
+                return get_generic_fn_type(ira->codegen, &fn_type_id);
+            } else {
+                zig_unreachable();
+            }
+        }
+        FnTypeParamInfo *param_info = &fn_type_id.param_info[fn_type_id.next_param_index];
+        param_info->is_noalias = param_node->data.param_decl.is_noalias;
+
+        if (lazy_fn_type->param_types[fn_type_id.next_param_index] == nullptr) {
+            param_info->type = nullptr;
+            return get_generic_fn_type(ira->codegen, &fn_type_id);
+        } else {
+            IrInstruction *param_type_inst = lazy_fn_type->param_types[fn_type_id.next_param_index];
+            ZigType *param_type = ir_resolve_type(ira, param_type_inst);
+            if (type_is_invalid(param_type))
+                return nullptr;
+            switch (type_requires_comptime(ira->codegen, param_type)) {
+            case ReqCompTimeYes:
+                if (!calling_convention_allows_zig_types(fn_type_id.cc)) {
+                    ir_add_error(ira, param_type_inst,
+                        buf_sprintf("parameter of type '%s' not allowed in function with calling convention '%s'",
+                            buf_ptr(&param_type->name), calling_convention_name(fn_type_id.cc)));
+                    return nullptr;
+                }
+                param_info->type = param_type;
+                fn_type_id.next_param_index += 1;
+                return get_generic_fn_type(ira->codegen, &fn_type_id);
+            case ReqCompTimeInvalid:
+                return nullptr;
+            case ReqCompTimeNo:
+                break;
+            }
+            if (!calling_convention_allows_zig_types(fn_type_id.cc)) {
+                if ((err = type_resolve(ira->codegen, param_type, ResolveStatusZeroBitsKnown)))
+                    return nullptr;
+                if (!type_has_bits(param_type)) {
+                    ir_add_error(ira, param_type_inst,
+                        buf_sprintf("parameter of type '%s' has 0 bits; not allowed in function with calling convention '%s'",
+                            buf_ptr(&param_type->name), calling_convention_name(fn_type_id.cc)));
+                    return nullptr;
+                }
+            }
+            param_info->type = param_type;
+        }
+    }
+
+    if (lazy_fn_type->align_inst != nullptr) {
+        if (!ir_resolve_align(ira, lazy_fn_type->align_inst, &fn_type_id.alignment))
+            return nullptr;
+    }
+
+    fn_type_id.return_type = ir_resolve_type(ira, lazy_fn_type->return_type);
+    if (type_is_invalid(fn_type_id.return_type))
+        return nullptr;
+    if (fn_type_id.return_type->id == ZigTypeIdOpaque) {
+        ir_add_error(ira, lazy_fn_type->return_type, buf_create_from_str("return type cannot be opaque"));
+        return nullptr;
+    }
+
+    return get_fn_type(ira->codegen, &fn_type_id);
+}
+
+static Error ir_resolve_lazy_raw(AstNode *source_node, ConstExprValue *val) {
+    Error err;
+    if (val->special != ConstValSpecialLazy)
+        return ErrorNone;
+    switch (val->data.x_lazy->id) {
+        case LazyValueIdInvalid:
+            zig_unreachable();
+        case LazyValueIdAlignOf: {
+            LazyValueAlignOf *lazy_align_of = reinterpret_cast<LazyValueAlignOf *>(val->data.x_lazy);
+            IrAnalyze *ira = lazy_align_of->ira;
+
+            if (lazy_align_of->target_type->value.special == ConstValSpecialStatic) {
+                switch (lazy_align_of->target_type->value.data.x_type->id) {
+                    case ZigTypeIdInvalid:
+                        zig_unreachable();
+                    case ZigTypeIdMetaType:
+                    case ZigTypeIdUnreachable:
+                    case ZigTypeIdComptimeFloat:
+                    case ZigTypeIdComptimeInt:
+                    case ZigTypeIdEnumLiteral:
+                    case ZigTypeIdUndefined:
+                    case ZigTypeIdNull:
+                    case ZigTypeIdBoundFn:
+                    case ZigTypeIdArgTuple:
+                    case ZigTypeIdVoid:
+                    case ZigTypeIdOpaque:
+                        ir_add_error(ira, lazy_align_of->target_type,
+                            buf_sprintf("no align available for type '%s'",
+                                buf_ptr(&lazy_align_of->target_type->value.data.x_type->name)));
+                        return ErrorSemanticAnalyzeFail;
+                    case ZigTypeIdBool:
+                    case ZigTypeIdInt:
+                    case ZigTypeIdFloat:
+                    case ZigTypeIdPointer:
+                    case ZigTypeIdArray:
+                    case ZigTypeIdStruct:
+                    case ZigTypeIdOptional:
+                    case ZigTypeIdErrorUnion:
+                    case ZigTypeIdErrorSet:
+                    case ZigTypeIdEnum:
+                    case ZigTypeIdUnion:
+                    case ZigTypeIdFn:
+                    case ZigTypeIdVector:
+                    case ZigTypeIdFnFrame:
+                    case ZigTypeIdAnyFrame:
+                        break;
+                }
+            }
+
+            uint32_t align_in_bytes;
+            if ((err = type_val_resolve_abi_align(ira->codegen, &lazy_align_of->target_type->value,
+                            &align_in_bytes)))
+            {
+                return err;
+            }
+
+            val->special = ConstValSpecialStatic;
+            assert(val->type->id == ZigTypeIdComptimeInt);
+            bigint_init_unsigned(&val->data.x_bigint, align_in_bytes);
+            return ErrorNone;
+        }
+        case LazyValueIdSliceType: {
+            LazyValueSliceType *lazy_slice_type = reinterpret_cast<LazyValueSliceType *>(val->data.x_lazy);
+            IrAnalyze *ira = lazy_slice_type->ira;
+
+            uint32_t align_bytes = 0;
+            if (lazy_slice_type->align_inst != nullptr) {
+                if (!ir_resolve_align(ira, lazy_slice_type->align_inst, &align_bytes))
+                    return ErrorSemanticAnalyzeFail;
+            }
+            ResolveStatus needed_status = (align_bytes == 0) ?
+                ResolveStatusZeroBitsKnown : ResolveStatusAlignmentKnown;
+            if ((err = type_resolve(ira->codegen, lazy_slice_type->elem_type, needed_status)))
+                return err;
+            ZigType *slice_ptr_type = get_pointer_to_type_extra(ira->codegen, lazy_slice_type->elem_type,
+                    lazy_slice_type->is_const, lazy_slice_type->is_volatile, PtrLenUnknown, align_bytes,
+                    0, 0, lazy_slice_type->is_allowzero);
+            val->special = ConstValSpecialStatic;
+            assert(val->type->id == ZigTypeIdMetaType);
+            val->data.x_type = get_slice_type(ira->codegen, slice_ptr_type);
+            return ErrorNone;
+        }
+        case LazyValueIdPtrType: {
+            LazyValuePtrType *lazy_ptr_type = reinterpret_cast<LazyValuePtrType *>(val->data.x_lazy);
+            IrAnalyze *ira = lazy_ptr_type->ira;
+
+            uint32_t align_bytes = 0;
+            if (lazy_ptr_type->align_inst != nullptr) {
+                if (!ir_resolve_align(ira, lazy_ptr_type->align_inst, &align_bytes))
+                    return ErrorSemanticAnalyzeFail;
+            }
+            ZigType *elem_type = ir_resolve_type(ira, lazy_ptr_type->elem_type);
+            if (type_is_invalid(elem_type))
+                return ErrorSemanticAnalyzeFail;
+
+            if (elem_type->id == ZigTypeIdUnreachable) {
+                ir_add_error(ira, lazy_ptr_type->elem_type,
+                        buf_create_from_str("pointer to noreturn not allowed"));
+                return ErrorSemanticAnalyzeFail;
+            } else if (elem_type->id == ZigTypeIdOpaque && lazy_ptr_type->ptr_len == PtrLenUnknown) {
+                ir_add_error(ira, lazy_ptr_type->elem_type,
+                        buf_create_from_str("unknown-length pointer to opaque"));
+                return ErrorSemanticAnalyzeFail;
+            } else if (lazy_ptr_type->ptr_len == PtrLenC) {
+                if (!type_allowed_in_extern(ira->codegen, elem_type)) {
+                    ir_add_error(ira, lazy_ptr_type->elem_type,
+                        buf_sprintf("C pointers cannot point to non-C-ABI-compatible type '%s'",
+                            buf_ptr(&elem_type->name)));
+                    return ErrorSemanticAnalyzeFail;
+                } else if (elem_type->id == ZigTypeIdOpaque) {
+                    ir_add_error(ira, lazy_ptr_type->elem_type,
+                            buf_sprintf("C pointers cannot point opaque types"));
+                    return ErrorSemanticAnalyzeFail;
+                } else if (lazy_ptr_type->is_allowzero) {
+                    ir_add_error(ira, lazy_ptr_type->elem_type,
+                            buf_sprintf("C pointers always allow address zero"));
+                    return ErrorSemanticAnalyzeFail;
+                }
+            }
+
+            if (align_bytes != 0) {
+                if ((err = type_resolve(ira->codegen, elem_type, ResolveStatusAlignmentKnown)))
+                    return err;
+                if (!type_has_bits(elem_type))
+                    align_bytes = 0;
+            }
+            bool allow_zero = lazy_ptr_type->is_allowzero || lazy_ptr_type->ptr_len == PtrLenC;
+            assert(val->type->id == ZigTypeIdMetaType);
+            val->data.x_type = get_pointer_to_type_extra(ira->codegen, elem_type,
+                    lazy_ptr_type->is_const, lazy_ptr_type->is_volatile, lazy_ptr_type->ptr_len, align_bytes,
+                    lazy_ptr_type->bit_offset_in_host, lazy_ptr_type->host_int_bytes,
+                    allow_zero);
+            val->special = ConstValSpecialStatic;
+            return ErrorNone;
+        }
+        case LazyValueIdOptType: {
+            LazyValueOptType *lazy_opt_type = reinterpret_cast<LazyValueOptType *>(val->data.x_lazy);
+            IrAnalyze *ira = lazy_opt_type->ira;
+
+            ZigType *payload_type = ir_resolve_type(ira, lazy_opt_type->payload_type);
+            if (type_is_invalid(payload_type))
+                return ErrorSemanticAnalyzeFail;
+
+            if (payload_type->id == ZigTypeIdOpaque || payload_type->id == ZigTypeIdUnreachable) {
+                ir_add_error(ira, lazy_opt_type->payload_type,
+                        buf_sprintf("type '%s' cannot be optional", buf_ptr(&payload_type->name)));
+                return ErrorSemanticAnalyzeFail;
+            }
+
+            if ((err = type_resolve(ira->codegen, payload_type, ResolveStatusSizeKnown)))
+                return err;
+
+            assert(val->type->id == ZigTypeIdMetaType);
+            val->data.x_type = get_optional_type(ira->codegen, payload_type);
+            val->special = ConstValSpecialStatic;
+            return ErrorNone;
+        }
+        case LazyValueIdFnType: {
+            LazyValueFnType *lazy_fn_type = reinterpret_cast<LazyValueFnType *>(val->data.x_lazy);
+            ZigType *fn_type = ir_resolve_lazy_fn_type(lazy_fn_type->ira, source_node, lazy_fn_type);
+            if (fn_type == nullptr)
+                return ErrorSemanticAnalyzeFail;
+            val->special = ConstValSpecialStatic;
+            assert(val->type->id == ZigTypeIdMetaType);
+            val->data.x_type = fn_type;
+            return ErrorNone;
+        }
+    }
+    zig_unreachable();
+}
+
+Error ir_resolve_lazy(CodeGen *codegen, AstNode *source_node, ConstExprValue *val) {
+    Error err;
+    if ((err = ir_resolve_lazy_raw(source_node, val))) {
+        if (codegen->trace_err != nullptr && !source_node->already_traced_this_node) {
+            source_node->already_traced_this_node = true;
+            codegen->trace_err = add_error_note(codegen, codegen->trace_err, source_node,
+                buf_create_from_str("referenced here"));
+        }
+        return err;
+    }
+    if (type_is_invalid(val->type)) {
+        return ErrorSemanticAnalyzeFail;
+    }
+    return ErrorNone;
+}
diff --git a/src/ir.hpp b/src/ir.hpp
index 3761c5a97d..3923ea28e8 100644
--- a/src/ir.hpp
+++ b/src/ir.hpp
@@ -16,7 +16,9 @@ bool ir_gen_fn(CodeGen *g, ZigFn *fn_entry);
 ConstExprValue *ir_eval_const_value(CodeGen *codegen, Scope *scope, AstNode *node,
         ZigType *expected_type, size_t *backward_branch_count, size_t *backward_branch_quota,
         ZigFn *fn_entry, Buf *c_import_buf, AstNode *source_node, Buf *exec_name,
-        IrExecutable *parent_exec, AstNode *expected_type_source_node);
+        IrExecutable *parent_exec, AstNode *expected_type_source_node, UndefAllowed undef);
+
+Error ir_resolve_lazy(CodeGen *codegen, AstNode *source_node, ConstExprValue *val);
 
 ZigType *ir_analyze(CodeGen *g, IrExecutable *old_executable, IrExecutable *new_executable,
         ZigType *expected_type, AstNode *expected_type_source_node);
@@ -28,6 +30,4 @@ ConstExprValue *const_ptr_pointee(IrAnalyze *ira, CodeGen *codegen, ConstExprVal
         AstNode *source_node);
 const char *float_op_to_name(BuiltinFnId op, bool llvm_name);
 
-void ir_add_analysis_trace(IrAnalyze *ira, ErrorMsg *err_msg, Buf *text);
-
 #endif
diff --git a/src/tokenizer.cpp b/src/tokenizer.cpp
index 84f3f2c0ec..9c9effcb10 100644
--- a/src/tokenizer.cpp
+++ b/src/tokenizer.cpp
@@ -841,7 +841,7 @@ void tokenize(Buf *buf, Tokenization *out) {
             case TokenizeStateSawAmpersand:
                 switch (c) {
                     case '&':
-                        tokenize_error(&t, "`&&` is invalid. Note that `and` is boolean AND.");
+                        tokenize_error(&t, "`&&` is invalid. Note that `and` is boolean AND");
                         break;
                     case '=':
                         set_token_id(&t, t.cur_tok, TokenIdBitAndEq);